Well, the only issue I see is that this system would tie what skills you could actually be an expert in to your class. That's just another way of removing the flexibility I'm looking for. Without that flexibility I don't really see the point. Why go through the effort of decoupling skills from stats only to then couple them to class?
Not to be flip, but that's pretty much the point of a class-based system: group capabilities into large buckets and move on with life. It's not exactly a secret, but it is something most folks don't acknowledge
explicitly. It's the trade-off made for the simplicity of the classes and you should go into that with eyes fully open.
If it really, really bothers you, I'm going to suggest checking out Savage Worlds. No sarcasm there. Just offering a workable option if you don't feel like the trade-off is worth it. Different systems exist for a reason. I'll admit to being of two minds about it, myself.
Could the core fear of my proposal be that yall are afraid that players will still flock to the max or dump skill allocation if we don't enforce something else?
Not for me. As I indicated, I just don't think there's much value in having more breakdown than "good, fair, poor" in D&D skills. It's one more fidgety thing to worry about and skill checks tend to be something of a side-show, in practice. IMO, it's actually value-reducing to increase the complexity any more than it already is.
If you want to decouple and tweak the way things work, that's cool. I love to tinker and am more than happy to try to get some sort of rules module up and running. There's a point at which you have to realize that you're fighting system inertia, though -- peeing into the wind, as it were. If you cause a cascade of changes, that's a bad plan because you've just changed the game enough that it's a genuine barrier to new members of your group. There's also a point where you start fighting core design characteristics of the underlying system, which means your module doesn't really work aesthetically, even if it works mechanically.
In this case, it would be perfectly feasible to grant all PCs a standard amount of skill points and then open up all skills to everyone. That might put some classes (Rogue) at a disadvantage, unless you tweak base points bay class. Regardless, you would be able to have a sneaky, fast-talking Fighter or a Wizard who was an amazing survivalist and animal trainer. There's nothing really
wrong with those concepts, but they start to break down class boundaries. Why not allow the Wizard to get Expertise in Survival or let a Rogue learn the Duelist fighting style? How about a shape-shifting Druid who taps into rage when in bear form? Very cool, but normally requires multi-classing.
So, just expand the feat system by converting all the class features into feats, with some chains and level requirements, for balance. Heck, you could even turn spell-casting into a feat chain, with feats that grant more slots, prepared spells, and access to new levels. A feat for each hit die bump would work, too. We've already got a pretty straight-forward conversion between skill points and feats (3 skills = 1 feat) and ability scores (2 stat points = 1 feat). Now you've got a point-buy system, instead of a class-based system. Give me 40 hours and I could write up a play test draft for you (maybe I should do that as a PWYW on DMsGuild and see how it goes).
One side effect is that we don't need character levels, anymore, since we have the finer grained advancement with feats. Proficiency bonus could be done away with, but then we need to add an attack skill or two -- otherwise, do some sort of tier system where every, say, 5 feats your proficiency bonus goes up by +1.
Regardless, this no longer resembles D&D, other than in some superficial ways and the ability to share some resources. You
could go through all that work, but it's probably better to just go ahead and play something else to begin with. Even if you'd prefer the alt-D&D, I wouldn't sell it to folks as "D&D". It's probably different enough that you'd be better starting with a fresh rule book and just letting people know they could borrow from D&D fairly freely.
Sorry for the long post. I hope it doesn't come off too rant-y. It's just some design thought and why going too far off course starts to get weird.