I have to say that any kind of "forgetting" of either RHD, LA, or both, can easily be broken clean in two when using fast-progression casting classes. My system is totally incompatible, I have to admit. (For example, you could get 60! points in ability boosts and then slap an Ur-priest on top of that, which is clearly the divine gish of doom. Or play a Beholder mage as a fricken beholder. Bad enough.)
The focus, I think, should be on the non-casters, though. Casters get all the fun and games, anyway. You don't want to give a full-caster a set of big ability boosts as well as 9th level spells, in my book. IF they want those nifty abilities, then they shouldn't also want to be a full caster. So the question of any system has to be: How can I help non-casters compete? And I think power races and templates could be the answer, while maintaining enough drawbacks that full-casters won't want to play them.
Look at it this way:
A cleric, while it clearly has some utility, will be strongest with its tone of buffs and then it can just slug it out with the bad guys. Clerics aren't finesse fighters, mostly brute force that works really really well.
A non-caster who could gain a batch of natural armour, immunities, ability boosts, good saves, and maybe an SLA or two can then at least keep up for a section of the relevant levels (I would say about 7-16, because ability boosts get really brutal at low levels.)