I didn't think Krikzz would ever tackle GBA. This will probably be the best flash cart of the system when its released.
No doubt it would be special, and I would be excited to see something a bit more available. However I am not seeing the room to do something especially earth shattering -- the NES has lots of mappers and annoyance, the SNES has its special chips, the N64 is not so troubled but it is not without issue and options for N64 flash carts were somewhat lacking, as were most of the others on this list come to think of it, the GB/GBC does have memory bank controller stuff but did not have a multigame focused device (all for LSDJ really).....
There are GBA flash carts though (there were ones for the others but GBA stuff ended up pretty mainstream), ones with basically full compatibility (or indeed all if you do not count the supercard, its clones and the very first attempts at GBA carts), ease of use and a focus on having multiple games and I doubt they are going to change that for the everdrive.
No doubt they could some damage if they coded a really nice menu -- savestates have already been demonstrated on GBA carts, multiple/selectable saves is a useful thing, if they can get it to drag and drop level then that is nice, if they want to include IPS patching support/autopatching for AP/hardware then great, if they want to have a solid cheat engine then OK. However in terms of hardware limits we are back to jokingly suggesting tilt sensors, solar sensors, the connections used for the Legendz series or giving me the option to pirate a glucoboy. Real time clock is mainly just pokemon, and not even all of them, though I would put those considerably ahead of even rumble support.