Maybe a Steam Workshop for mods? I didn't know there were mods for this game, and that would help find them easier. :) Dev don't want to be tied to steam, the game is released on their website, GOG, Humble store and steam, supporting steam workshop will only benefit steam user. That's why, there is...

Idea, can you make a tunnel like an underground belt, but for the player to get around a big factory or the solar panel fields; so the player won't have to go around. Also, making a teleportation structure or portal so the player will be able to teleport to far away areas. Maybe a Steam Workshop for...

Shields for the Tank, or make Armor plates with a size of "1x1" like the solar panels, but with adding armor.
A better Engine that will allow the tank to go faster.
A better Engine with more fuel efficiency.
Flamethrower on tank and more weapons for grid.