The one time I ever played a character with level adjustment, I didn't actually use it correctly; I didn't count hit dice into ECL, just the LA. It still wasn't that strong a character, sadly.
I do spend a lot of time thinking about how to 'fix' level adjustment, though; I mean, less levels mean less hit dice, less skill points and lower max skill rank, less feats, weaker saves and BaB, lower caster level and less spells. Strength, Dexterity, Wisdom and Charisma improve your stats linearly and so only offset the effects of lost levels, while Constitution and Intelligence have multiplied-by-levels benefits and so are greatly weakened by less levels. The only things that might be fairly certain to get a net raise are AC, melee damage, and spell save DC.
Mm...though now I think about it, having a rule against 'no LA greater than half your ECL', using ability scores to offset lost level benefits and having racial features make up for lost class features could still work.
Hey, is there a rule that you HAVE to have the monster hit dice on some of these creatures? Or can you play centaurs with no racial HD?