Oof, this is interesting. I think first and foremost I’ll say “If it’s not a problem, it’s not a problem”, but given that you’ve come here, it probably is a problem in some way. I’ll also mention that ordering off-menu is definitely a privilege and not a right. We’re not talking about subsitutions, we’re talking about straight up “can the chef of this itallian restaurant make me an enchilada?” here. Sometimes you’ll get lucky, and there’ll be some spare tortillas back there, but it shouldn’t be an expectation.
I don’t want to be pessimistic but it sounds to me like your goals are at odds. PbtA is about very directed experiences, and wanting that to be both crunchy and unconstrained is kind of at odds. PbtA is by definition a very constrained system. I don’t want to be so reductive though.
I think there’s a really interesting question about “okay, how weird are we talking, here?” There’s a spectrum of “violating conceit” that can occur, and while all of them are workable some are definitely more work. For example, in a Dungeon World game, a player that wants to be a parasite that has taken control of a human host is easy. Fictionally tag it, play a human fighter. Go for it, mate. Alternatively, a player who wants to play a time-traveling robot sent back to murder the mother of a resistance fighter in Burning Wheel requires significantly more work, to the point of drafting up a whole new subsystem and a stack of life-paths.
The reason I ask is that…well, there’s a real question of who’s doing the work here. Some real the customer is always right shit (see above re:Italian enchiladas). If you’re setting up the prep and the game and the GM duties and all this, are you also expected to write the new rules and the subsystem to cater to their varied needs? If as a group you’ve decided to play X, why is it anyone’s role but theirs when they want to play Y? (And again, if this is work you love doing and can sustainably do, this isn’t a problem. But the OP makes it sound like it is?). If they want to violate the conceit of the game, why are they so uninterested in engaging with the rules in a way that benefits them (as in “not very interested in reading lots of rules or almost any”), and expecting you to fix it? I’m sure they’re lovely people and very good people to play with, but it sounds like they’re asking a lot.
Then inevitably more than half the players want some wild shit that isn’t one of the playbook.
It sounds like you’re all deciding to get pizza, then half the team are ordering steaks. My suggestion would be: They didn’t really want pizza in the first place. If you lay out the playbooks of any (decently written) PbtA game, and they can’t see a character type they want to fit, they don’t want to play that game, in my opinion. They just might not have the words to describe that.
I wanna stick with this pizza analogy though (jeez I must be hungry with all this food talk): If you all agree that you’re going to buy them pizza, or you’re all going to pitch in or whatever, and someone says “I want McDonalds”, like, dude that’s fine, but you can organise your own delivery. We’re all getting pizza. Now, if the delivery lines up, you can still eat (play) together, but if your pizza arrives in thirty-minutes-or-less and the Maccas takes an hour (ie if your game and their character are wildly different in tone, agency, or goal), then either you’re gonna eat cold pizza, or they’re gonna be pissed you’re eating without them (ie someone is going to be disatissfied).
If more than half the table wants McDonalds, like maybe you just get that instead. Or if one wants maccas and one wants Hungry Jacks, and one wants curry, and one wants a kebab, and then there’s two of you waiting on Dominos…like maybe you need to choose between eating together and getting exactly the meal you want?
What game handles spotlight fluidly, is easy to GM, allows for wild and unique crackheads PCs, while still providing enough direction and crunch to feel like a game rather than total freeform?
None well. Very few at all. Crunch is a function of choice and direction. Fluidity is a function of shared intent. Both are at odds to “but I want to do something different”. As much as I love your goals and your intent, I think you’re going to be really disappointed with most anything that lands at your feet. I do hope I’m wrong and being reductive. Good luck to you!