Definitely some cool ideas there but how do you deal with the long term effect of the map becoming too big?
The bigger the map the more the defs would need to stretch their resources to adding cool stuff.
Also, at some point, the inner hexes will be essential all complete cleared and new players will have to wander for a while as soon as they level up a bit.
Unlocking a new hex would be fun at the beginning but how fun will it be after 100+ have been unlocked and any more just will inevitably just feel same-y because even the best defs will eventually run out of ideas