Well, I was bored and playing around with modding. I've mostly been fiddling with the ship models, when I notice there are several "models" with the same name convention as ship hulls.
And guess what, it works too!
Just paste this below into your GC2Types.xml, start a game as the humans, and marvel and the wonderous force that is the little guy marching through space... Just need to strap a particle cannon on him and away we go...
There are a few other models too. I can see the soldier, tank, troop carrier thing all from the planetary invasion animation (which seem to use the same modelling procedures as ships, interesting....) and a few other mysterious hulls.
Link