As an aside, why is it not any more difficult to disarm a weapon physically built into a mecha than it is to regular disarm a weapon that is merely held in hand? I mean, imo, if disarming a built-in weapon is possible, its kind of akin to trying to disarm a weapon from a locked gauntlet or something, no?
A not-in-built weapon isn't "merely held in hand", it's tightly clamped by metal manipulators that were designed specifically for that purpose. If you can pull a weapon from that, pulling a weapon physically built into a mecha isn't really harder.
In mecha battles "disarming" should be taken to the literal sense that a limb's been chopped off. As talked previously it's a staple of mecha shows, giant robots get bits chopped off left, right and center. Luckily mechas don't bleed off and even a chopped limb can be quickly fixed in a base or even jury-rig something on the scene (move action to "pick up" disarmed weapon).
Also again rule of cool, mechas holding weapons in hand should be as viable as leg missiles and shoulder cannons and whatnot.
Well, to a degree it makes sense because mecha have a tendency to lose arms and everything else.
But then it goes back to 3.X being all about size for combat manoeuvres and the best way to deal with them is to be big. And if you throw enough attempts in, eventually there's a fail... which is a pretty big deal when it comes to how limited weapon replacement is.
Cough Tek Knight cough. Also Gun Maniac and Martial Machine have some maneuvers to help make up for size differences plus some T.O.U.H.O.U. stuff.
And that is, in point of fact, the only REALLY good option for Tek Knight...
No, seriously, it has the least hideous drawbacks. If you're looking to maximize combat maneuvers as a tiny mecha you're probably getting up close and personal anyways, so arsenal halving is just *shrug*. Point for point some of that stuff is just not worth it. Great Plating and whatnot is a really nice option, why? Because when your Dodge bonus is 0, then you don't care that it gets cut in half. By contrast, consider Tek Reactor, which gives you +40 energy but halves your spirit points, at a whoopin' 4 point cost. In order to make full use of size benefits, you'd have to invest 8 points in it for a total of +75 max energy. By contrast, for 5 points, you could have Reactor 2, which would get you an average 11 points of energy each round with no drawbacks and spare you three upgrade points. Taking Tek Reactor effectively makes certain higher-level Super spirits unusable. Tek Soul, by contrast, makes some low-level spirits spammable (sort of), but max HP in half is... yeesh. Better hope no one gets through your every-single-round Alert, buddy. Tek Storage is... okay, I guess? Sort of? I mean, if you want to be a tiny, tiny kinetic weapons platform, then the energy halving isn't so bad. I honestly don't understand why you can't have Nanomachines along with it (Mysterious Power makes sense though, since less energy is less of a problem if every round regen is making up for it).