So I guess you would dig playing one of the Scoobies in the Buffy the Vampire Slayer RPG then

?
Zeppo, CPR, and eye patches.... Bring it on!
Honestly, it depends. We have this whole RPG legacy with its roots in LotR. Playing Frodo as presented in the actual books would SUCK way more than any supporting character in Buffy. And yet it adapts quite nicely.
I have said in other threads that I find balance to be important at the PC to PC level, but I don't worry about it nearly as much when it comes to encounter by encounter balance. So the idea of a Xander character being a limited support in a particular encounter does not make me bat an eye. It is no problem to keep contribution and even just the fun of being involved persistent in the game for both the Slayer player and the Scooby player, so everyone is having fun and, if the there is a way to win then that is the very definition of "winning" the game.
It certainly requires some higher level of skill from the GM to run a wider range of players. But a little-leaguer not enjoying or benefiting from a fast pitch hitting machine is not evidence of a flaw in the machine.
I'm sure you could reach some extreme disparity that would be pointless. But we are talking within a PF thread with legacy 3X as a reference. I don't know of any classes that come close to the Xander / Buffy disconnect and even that disconnect isn't bothersome to me. So I don't see a greater disconnect as relevant.
Or maybe running a RIFTs game would be more of your thing?
Never played it. Don't know.
That's your problem there. 30 splat books is way, way too much. Once you get over 10 books, you're just asking for trouble.
I've got over 50 3X books within steps of where I'm sitting. I guess trouble doesn't like me because apparently I'm beyond asking and well in to begging, but still no trouble.