I think if you put new things like, Pve or Pvp mode online or new levels, new tanks, etc... This game can be very popular, keep it going :'D
To add to number 3, better air control would be appreciated as well. Currently, you can slightly alter the tank's rolll and pitch while mid-air with WASD (caused me some confusion at first, because the tank kept flipping upside down after every jump due to me holding W).
I don't think Rocket League-levels of control is necessary, but just a tiny bit more control would be nice.