I'd like to see level adjustments go away and the strengths/weaknesses of a creature equal to their HD (something 4E is actually doing right). Templates would add HD of the creature type, so a half-dragon would add ?d12 HD. The problem is giving a balanced HD value equal to the strengths of the LA. I think 2 HD per LA should work for most templates. So a half-dragon would add 6d12 HD to the existing creature.
This doesn't work too well with PCs and templates though. What happens if a character becomes a lich or contracts lycanthropy?
Something like a minotaur (6HD +2LA) would either still be 6HD but a little waeker to make it equal to a 6th level character, or take it up to 8HD.