Larger mechs should have the Tek's Storage and smaller mechs should have Great's Agility.
I'd say that speed is something more common to bigger creatures than smaller ones. Large core creatures often have a speed of 40 ft while smaller ones have a speed of 20 ft, for example.
I'd say Great Targeting for smaller creatures would make more sense, since big stuff get a size penalty to hit and smaller stuff get a bonus instead. Easier to be precise when you're smaller. Keeping it a Great One ability is better for my comp, though. It does feel like more arsenal/hardpoints for bigger stuff may make sense but usually equipment size is proportional.
Super Servos: Should it not be +1 per pick? The bonus to Disarm would stack with Target's increase to attack rolls, by the way.
Great One: Something I've noticed. They all get about an equivalent amount of effective super upgrade picks at medium size, but the equivalent number of bonus super upgrade picks per size increase isn't the same from one size increase to the next. Which means that some Great One picks are much more cost efficient than others.
For example, Great Agility is twice as efficient as Great Plating and Great Targeting is about twice as efficient as Great Agility and four times as efficient as Great Plating. They should all be equalized if we go with the premise that the upgrade point options are all of equal worth.
Great Plating- 4x plating +dodge bonus halved. /+~half plating /+~1x plating /+~2x plating /+~x3.5 plating
Great Agility- 4x agility +natural armor halved. /+agility /+2x plating /+4x agility /+~7x agility
Great Targeting- 4x targeter + DR is halved. /+2x target /+5x targeter /+9x targeter /+14x targeter (wut!?)
Assuming these extras per size are not cumulative. It isn't clear.
Tek Reactor: 4x battery + but max Spirit is halved. + half battery /+1x battery /+2x battery /+3.5x battery. ; It follows the pattern for Great Plating. All good.
Tek Soul: 4x SotM /+1x SotM /+2x SotM /+ 3x SotM /+4x SotM. ; Upgrade point growth is superior to Great Plating/Tek Reactor. Also, careful with putting the HP halving at the very end after the growth for Fine, especially when only separated by a comma. It looks like it applies only to fine sized mechas, which is clearly not intended.
Tek Storage : Before all else, I'll point that I do not think that having an upgrade of this kind for hyperdimensional storage is a good idea. Mostly considering that the value per point does not compare with the others since it can only be picked once per 4 pilot levels to begin with, which means that no matter what you get there the value is immense.
Consider, the default value is 2 hardpoints and 25 arsenal space. That's worth 3 hyperdimensional storage picks which requires 12 levels in super pilot by default.
The value per pick is exponential as well. 3 picks is worth 1+2+3 = 6 upgrade points. You spend only 4 upgrade points for this bundle.
Then you get an extra pick and almost a half the next size category, which is worth at least an extra 4 points for a total of 10 before further size categories. And that is all assuming that hyperdimentional storage upgrade points aren't taken on the side as well, which you can be is the case considering the worth per point pick of Tek Storage doesn't affect them, effectively increasing the point worth of Tek Storage to 9 at medium pre-super pilot level 8, a worth of 14 points pre-level 8 at small size, a worth of 12 points at medium size for levels 8-11, and effectively 18 points at small size for pilot level 8-11. A level 20 super pilot could normally not get more than 4 hyperdimensional storage picks for 10 points. This is nuts.
Tek Servos: 4x pick for half arsenal (which is a strange thing to halve considering that arsenal space isn't something they get much of by default anyway, essentially driving the pilot to just get Nanomachines/Mysterious Power instead). /+~2.5x pick /+~3x pick /+~3.5x. Strange progression rate. Better than Great Plating/Tek Reactor at some size tiers.
Zero Arts +1 pilot level and DC, which increases every 4 super pilot level. This is already pretty darn good by itself compared to the other Great/Tek upgrades considering the worth and rarity of the stat it increases. I think it is well worth the 4 upgrade points as is. Further, I'll note that, just like normal size increases/decreases, the Great and Tek upgrades have advantages and disadvantages, usually in the form of halving another stat. The Zero abilities have no penalty whatsoever, which effectively makes them twice as good. Plus you don't have to pay extra upgrade points to access the improvements even though the increases are more linear than exponential. Not good from a balance point of view. This means that, for all the Zero abilities, unless they are weaker than their Great/Tek counterparts, they are overpowered by default.
Those extras would also be worth a feat each. Another impression is that as is they make Super Robots superior to Real robots. They scale much better.
Zero Entropy Let's see, each pick of Alien Alloy grants 10 resistance and reinforced +1. So resistance 5 being half of what is granted before the extra ability this would be sort of a quarter Alien Alloy pick. 1d6 deals an average of 3.5 extra damage when Great Power grants 4 damage, which can improves with weapon upgrade synergy, but has an halved stat penalty. Then add an auto damage aura. I'd say this ability too is as good if not better than a Great/Tek equivalent before the extra abilities.
Which would be overpowered even if they were a feat each, by the way.
The perpetual fog is very good though at least there is an arsenal counter provided within the same setting's material.
Zero Range is very, very good considering the low range of most of the arsenal and built-in weapons provided to the mechas by the setting itself.
Zero Speed is crazy. You the radius of the ability gets pretty big. At level 12 this is a 120-mu aura that sets the speed of everything else down to a quarter. So something out of your aura needs to travel at least 480 mu to reach you. Assuming there isn't fog on top that which you cannot see through since that would further halve your movement. A charge could be made with a speed of 240-ft, but that isn't within the range of most mechas at that level. The gains vs cost of the ability are just way too good. The aura just gets way too large for an overpowered extra that isn't even needed for the ability to be on par with the similar options to begin with.
Personally, I'd say that this ability should not be a super upgrade. It should be something else entirely, such as a prestige class ability, maneuvers or similar. I'd say the same for most of these Zero Extras. They don't feel like they belong with the rest of the kit.
Zero State: The nerf makes it a lot harder to abuse but the potential is still there. The worst is taken care of by preventing copies from making more copies the same turn, still. I'll note, though, that even a single copy is amazing if only for the action economy value. For the same reason that Ancient Temple boost that creates a copy is so darn strong. It can multiple an entire combo.
That said, here is what I think of the mechanics of the ability itself;
When the cloning is done, the two copies generated appear adjacent... but adjacent to what? To the original pre-split robot or adjacent to each-other? The former allows them to appear with distance between them.
Soro figured it out as well (
); Indeed, the pilot should not be copied. It allows a plethora of abuse options common to any other effect that makes a copy of the user... but there is also abuse potential in the fact that it specifically copies the "main pilot", rather than just the pilot. Someone piloting another's super robot with this would be able to make a clone of the original pilot of the super robot with this ability. The ability also copies only the main pilot and the super robot, so any passengers and items stored within the robot aren't copied - the two copies of the original split thus infer that those stored objects and passengers drop off to the ground at the spot the original split from. It also provides a source of sentient sacrifices off the copied pilots. You can also get the copies to form a mob you can then lead, thus bypassing quite a few penalties. You can also have the copied pilots leave the mecha for other tricks and get the Sentient upgrades to get a bunch of mecha copies that still follow your commands. I could go on but I think you get the point.
The ability also assumes that the user has control over the copies.
The ability also has a lot of utility outside of combat.
I've mixed feelings about Zero Circuit. It has OP potential despite the restrictions but they really help and tuning it down.
Otherwise, perhaps a range limit between the copies would be required. It makes "adventuring from the comfort of your home" by sending a copy to do the quests for minimum risks very, very tempting despite the more fragile state of the copy doing all the work.
Zero Weapon: This one's a bit trickier to gauge. Kind of like a partial Super Servos/Agility/Plating with a bonus to saves, which has no real upgrade equivalent but we can guess it would be a costly one since it would be at least one upgrade per +1 bonus to saves. It depends on specific weapon usage, however, which diminishes the worth a slightly. As such, the original worth is indeed at least what one would expect of the original equivalent worth of a Great/Tek upgrade. The ability scales with pilot levels as well in a linear fashion, and does not actually have a penalty either, so it, too, is already on par if not superior to them before you even add the Extras.
Absolute Barrier: Considering that this is available starting at level 1 and that mechas now mostly begin with 100 energy, I'd say that in most cases this is superior to Gravity Wall. You also get a remarkable immunity as an extra, some of which are pretty darn rare and very difficult to acquire otherwise. Plainly OP, especially early.
Late game it is easier to work around using all the tricks that work on those energy shield abilities, but those are harder to do early game and it may get boring to play who breaks the other's shield first/who runs out of propellant packs first.
As an aside, I recall the Zero Range passive in PSO2 to be a ranged weapon option that makes them hit harder when you are close to the target. You make them get better range.