Great question. To be honest, adding mod support is really hard -- significantly harder than just making a robot fighting game. That being said, we are doing as much as we can to push in that direction:
1. Users already have the ability to create custom shapes in the BotLab, and to store and share their robots via .RR2Bot files. Since the files are text-based instead of binary, it is possible to go in and change the robots by hand, or to write tools to automate the process.
2. In addition, this week I am working on BotLab texture generation and saving. By the end of the next week or so, I am hoping to have a system in place for creating custom textures, saving them to a file, then loading the back into the game.
3. Once user-created textures are working, we are hoping to explore the ability for users to import UV-mapped .obj files in something like Blender or 3DS Max that they can bring into the game as custom shapes. If this works, a user with sufficient 3D modeling skill should be able to create parts for any robot they want, texture them in an external program, then bring them into the game.
We are DEFINITELY going to do #1 and #2.
BIG CAVEAT - #3 is entirely aspirational at this point.
I hope we can get to #3, but at this point our first priority has to be getting BotLab robots fighting each other. We are a really small team, so any hour we spend working on a modding feature is an hour not spent working on the core game. The core of the game has to come first.