1)im not sure if i should create an issue for eache feature or an "feat request" issue
there are an anime called "attack on titan" or "Shingeki no kiojym" in japanese where the characters use arrows + ropes to do 3d moves on the battle field.
if that system was real it would be hard to use. flapy bird is ridiculous hard there are puns with the 2 on the internet but no game at all
http://cdn.i.ntere.st/p/9205522/image
so a game could make sucess.
there are an "flappy generator" out there but it can only replace bird/ pipe images for something else, the ropes cant be made with just that (you will need trace an line between the player and the pipe) and the phisch control will need some changes (but it can be only an visual change with the same phisich instead)
2)add an "ask a feature" donation button
its hard to make money with open source, maybe you can put an "vote on a feature" where the more money the person donate the more votes he can give .
and any one can ask a feature but only features classified as possible, can be voted.
I was going to code this "ask a feature donate" thing but im not sure if there is one already avaliable.
3)power ups, moving pipes, and instead of arcade system *beat your record" another game modes such as won the level, with save points on the middle of the level.
something like this:
http://www.youtube.com/watch?v=YHH2101OFfI