Thats just too much work. Use the arty they give you, failing that nuke it from orbit, failing that throw a planet at it. Failing that go home and use a Cybran.
Back in my day we had something worse the walls, shields, more importantly cybran shielding. *insert ranting about how good supcom is and how this game needs sheilds*
I just realized, there aren't that many games where "nuke it from orbit" is a valid solution to a problem.
When enemy build walls, i build subterrainium units. Oh right not in the game "yet". wasnt it C&C Tiberium sun that had underground units. freaking hilarious concept.