HHHHhhmmmm, I'm not sure, Adaptive does mean that they are better at changing during a game, and to me this does not seem to be what you have chosen to do.
You have given some leaders the Variable trait, which means one aspect of their abilities can change each game (which is a great idea for them civs that only have one leader) I like it, keep it.
But, maybe you should also add an Adaptive trait.
Adaptive trait: I don't think it should mean you can change traits during the game, as this makes them very very powerful. Also, how would it work, do your unit loose their ability to move faster or resist magic that they gained when you had the trait. No, all seems to powerful and complicated.
Adaptive: Ability to react to new situations and come up with a solution quickly. Maybe this should be a unit ability and a civ ability.
Adaptive unit: Gains a free promotion adaptive. This gives the unit.... not sure, maybe they count all terrain as half movement penalty cost, or get the tile terrain defiance if they have been in tile for two stationery turns (so hill or forest or desert) or they upgrade and 2/3 cost. All these show the ability to adapt to a new challenge
Adaptive Civ:
No anarchy for changing civs (they take to new ideas quick).
Pay half the cost for civ upkeeps. Or maybe they get the most expensive civ for free, or just on civ for free
Adapt to adverse conditions better than most civs, and have half the negative city effects (so, can deal with overcrowding better, adverse buildings and not having their religion in city)
These are just my 15 mins at work thinking, what do you think.