Elites

If the upkeep is even higher than tier 2 then probbably not. as again what would be the point? If I can build 2 or even 3 basic units for the price of 1 T3 unit then with most unit types it'd be better to use the T1 units for speed. also elven wardens have speed 6. wardancers have speed 8 therefore T2 is already better valure for attack and are already faster.
But still with a different implementation its a good idea...

I personally think that what T3 is good for should vary from race to race. Fast T3 should either be given to elves or orcs only, or both. Dwarves should get T3 units of all types that are only good value for defence and perhaps only useful in mountain terrain.

Hmmm....yes.... now I think about it I totally agree with the dwarves bit as that would seriously over power dwarves as they'd be good at defending themselves and fantastic at siege. Humans too should have more balancing units as humans are generally a balanced race in most games. however your statment that "elites should not complement strategies that are already well-suited to a race" I couldn't disagree more. The races should be further diversified so that elves become even better at all things magical (when they come out). humans should be the most balanced of all races but have no main strength, Orcs should be generally good at attack.
Perhaps dwarves with their superior knowlege in the craftmenship of walls and siege equipment could have T3 units which are good at attacking walls.
Perhaps it could work like this. If 100 T3 units are in an attack against a level 20 wall then  100 defending units with the highest defensive values will only recieve a defensive bonus equivelent to a level 15 wall.
This is unlike orcs which will be the best race at "sally forth" or attack not involving walls.