Okay. You did NOT say that only one base class gets advanced. You just said "it's like gestalt". How am I supposed to intuit that this means "only a base class and a PrC" from that? Okay, with this new information, what I said still stands though, but it does mean the gap doesn't widen as much. Still though, what about Mystic Theurge? Now it's level 29 casting in one class and level 13 in another (or something). It's not as good, but that's still a RIDICULOUS power increase, getting level 9 spells at level 11. Or, if that's not how you intend it to work (maybe eliminating dual-progression PrCs, another thing you would need to specify), single class Wizard/Incantatrix. Heck, you made those PrCs that attempt to balance themselves by eliminating spell levels obsolete, now they are even more powerful.
When creating a new rule, you MUST think of any way it can be misinterpreted, and attempt to counter that misinterpretation preemptively. We are not inside your head. I used to have that problem with my writing (I still do, but it's not as bad now). You cannot assume that we understand implicitly that you intend only one base class to be advanced at once, just by saying "like gestalt". That could mean that you get the benefits of the classes that you take together, or it can mean two base classes, or it can mean that getting the same feature at the same time means you only get one version of it, or even something else.
Here's your problem in understanding. Fuck semantics, I don't care how you will name it. But the fact is: Casters (the high tier ones) get something, something very good, at each level. Spells. Spells are powerful, it's what makes tier 1s and 2s... well, tier 1s and 2s.
you're saying what? That casters can have PrCs that fully progress their only most powerful feature plus give them some new cool (or not) features in place of their dead levels, but mundanes can't have that because their levels are full of features? Is that what you're saying? That's bullshit man. Monk has a feature at every level and yet he's the worst class.
Am I seriously the only one left who thinks semantics are actually important? I mean, it's the difference between "and" and "or", if you're given an option, and they say "benefit a or benefit b", vs "benefit a and benefit b", there's a MAJOR difference in what you're getting. That's why semantics are important. If the meaning of a statement is determined by the semantics, then smeantics are immportant. And in the case of what I've been saying, yes, they are very, very, important. Class ability=/=flass feature. This is important to my argument, therefore you cannot simply ignore it, as doing so ignores what I'm saying, it does not reflect well on you.
Funny. This is almost the same as normal gestalt, but instead of Class//Class you have Base Class//PrC.
Here's the thing. Regular gestalt also exacerbates the caster problem. Or rather, it does not adress it, and casters can become more powerful by takin on another casting class (cleric//wizard, for instance). And then mundanes can also take caster (a nice thing I played once, I had fun with was cleric//monk). But does that fix casters? Or mundanes? No, it does not. It makes the monk better.....by pairing cleric with it. That's not making the monk better, it's just having two classes. The monk is still just as bad (and actually is not the worst class, that goes to CW Samurai, which is barely better than the NPC class Warrior, the monk is actually not as bad as most people claim, still worse than fighter though), cleric is still just as good.
Actually, that brings me to my next point I've been saying for a couple posts now: POWER DOES NOT EQUAL GOOD DESIGN. Actually, overpowered classes tend to be poorly designed, though this is not universal. I gave three well designed classes and three poorly designed ones from different tiers: monk, warblade, druid are well designed, tiers 4, 3, 1 respectively. Fighter, crusader, psion are poorly designed, tiers 4, 3, 1 respectively. Design relies on making the class desireable at all levels through flavorful, useful abilities. Balance comes in to play, but mostly to make sure that it is balanced within the same class, not with regards to other classes. It can be overpowered and still be balanced with regards to class design, this mostly means that you have a stead rate of power increase from 1 to 20, rather than a "suck from 1-5, rock from 6-12, insane from 13-20" deal.
And no, I'm not saying that casting PrCs granting full casting while mundane PrCs don't advance base calss abilities is good. I have not been saying that at all. I'm saying that it is a problem with how the BASE CLASSES are designed, and how the PrCs handle how poorly designed they are. Wizards need to be better designed, and PrCs need to handle it better. And yes, that is saying that I think wizards, the class, need to be completely, ground up, redesigned. Traditional spellcasting needs to be ground up reworked. Every /day caster needs to be reworked.
Now, how this pertains to your system. If you want this system to work as intended, you will need to rework every mechanic of EVERY CLASS so that it works with this. Now, which is easier, reworking every caster, or reworking every class and creating a new PrC system? Otherwise this is just a quick fix that doesn't actually change anything. Casters are still casters, mundanes are still mundanes, only now casters can have their PrCs and casting too (partial progression casting PrCs now become full, that's just straight power, wizards, psions, and druids distance themselves from the others with actual class features), and mundanes become not unlike the Monk, lots of abilities that just don't do anything. And actually, it was better for mundanes to have any PrC advance all base classes, that might have actually helped them in a significant way, though again, it helps casters more. You want this to work? Try looking at what the actual issues are, rather than seeing a bunch of abilities and thinking "that means power". That's the mentality that led people to thinking the Monk is a bad class. I'm actually curious, I want you to tell me why the Monk is bad, power wise.
Yes, believe it or not, it's hard to actually design a game, especially one this complex.