Relic did release the object editor at one point, however it was recalled pretty soon after due to not having any documentation, meaning nobody really know how to use it, even though a few hardy modders did. So, now they are hopefully going to release a new full version with documentation on how it all works. The OE (object editor) lets you attach animations among other things, so right now we could put a tank ingame, but it cant do anything so to speak, the OE would allow us to give it animations and stuff so it act as a proper unit.