I've got some ideas to your game:
1.extend grow size limit, because 1800m max is very small in my opinion
2.extend endless mode map, because it's also small
3.add a new evil giantess mode where you are starting with normal size and you have to defeat people for exp and then smash them or eat (I really want eating in this game) with higher size and later you will be able to destroy or eat buildings for more exp (you can also make it looking like taking a ground with a buildings on it) also add tanks and public transports and other transports to this gamemode like planes,busses,tanks,ships and etc. Which of course will give you more exp. And make the city very big to let the giantess reach the size like of 3000 meters tall. The game will end after destroying the whole city
4.make a breasts attack (it will look like a giantess is falling on her breasts and maybe if you would like you could add moving in this position aswell)hotkey:b
5.add more feelings to giantess
6.add rolling attack. (It will look like a laying giantess that will roll to the right or left side) hotkey:h
I think it's enough from me, tell me is the idea good or bad.