How would you affect fog cloud, stinking cloud, grease? The suggestion reminds me of pathfinder in some way.
You know, those guys have their heart in the right place.
Its just that their head's in their ass.
In any case, you can sort the problem spells into several layers, each sort takes it's own solution.
Open Ended solutions: Polymorph, Planar Binding, Shadow Conjuration, Wish. If theres a problem you can't solve with one, you probably can't solve it, period. These spells need to be split up or restricted in breadth, e.g. making Polymorph allow you to pick from a predefined list of special abilities you can copy with it.
Irresistable Forces: Solid Fog, Walls of Force, Wings of Cover, basically you can't do anything about these spells unless you have their specific(and almost always magical) solutions. These either need ways to resist their effects or for ways to bypass/demolish them to become more common.
Sidelong attack: Grease, Illusions, these just take unexpected approaches. Not really a problem.
X or Lose: Less a problem with the spells and more a problem with the concept to begin with. Don't touch these unless they fall under one of the other effects or you're fixing the whole save or lose business while you're at it.
Bigger Numbers Than You : Polymorph(again), Divine Power, and to a lesser degree the Hours duration stat buff spells. These basically give you bigger numbers than you should have for the level or else inflate wealth by giving you essentially staple buff items for free. Other than Polymorph(hello Hydra) and Persisted spells, this is more a case of getting mundanes the same size of numbers.
Extra Actions: Do I really need to explain these?
Trap spells: Yes, spells can be messed up in the other direction too. These are the Hold Portals(and to a lesser degree, Lightning Bolt and direct damage in general) of the world. Maybe give some of these out for free or something.
edit: my god this thread moves fast.