Hi!
I think that these are the new things that you could integrate:
- New harversters
- New ores
- Dungeons for killing boss and drop rare stuff
- Build a little shuttle to go in other maps/worlds
- New type of buggies with different speed
- Martians? Enemy Aliens -> Defence stuff like turrets, traps, and laser pistols.
If you need help, new ideas and other.. i'm available. Please don't stop development!