I definitely look forward to this when they added abilities to the game. Brad has said it is being looked at. There is currently no ability in the engine to retroactively add abilities to units but it is possible to rewrite that section of the code at a later date when they can set aside the time to do it. Rough estimate of three weeks of work to do it but that was probably said on the fly don't hold him to that schedule.
I think the game needs that change.
The tech tree should be sectioned off a bit more than it is with some cross referencing between the research types so you can't go straight to full powered bows and then the up your groups and kill everything with some magic items investment but some definite tiers where each type of tech stops until you unlock specific techs in civ war adventure magic and diplomacy - era's of the foundation of your kingdom some sort of equivalent thing to:
"Admantium/Elentium/Mithril - insert godly might- Age"
give some warning to the other players/ai when someone is advancing into another age.