OpenRA

This can be done easily, without any programming. Our unit definitions are specified in the yaml files in the mods/*/ directories - you just need to merge the different mod rules together, and then apply some tweaks to tell cnc units to use a custom palette.

If you're serious about creating a mod to do this, join us on IRC after the current rush has died down, and we can point you in the right direction.

If you can wait a couple of days, we will post a tutorial on how to create a basic mod. In the meantime, i suggest you take a look at the various yaml files in the mods directories to see how the different things are defined.