I think the mod tools will be powerful enough to add siege type units for sure. The Doms2 modding ability was very good imo, and it will be even more powerful in Doms3 as we all know.
"Training is principally an act of faith. The athlete must believe in its efficacy: he must believe that through training he will become fitter and stronger, that by constant repetition of the same movements he will become more skillful."