The thing about terrain is, so long as there is some clear terrain with in a few miles of the battle, you can still lob your missiles in. You don't have to be right there in the heat of the action like an LRM mech does. So the only time a Catapault really has a bid edge is when you need to hot drop it, and that seems like a dicey move, especaly considering the implications of deploying a unit with only five rounds for its gun with out imediate support.
I can't think of what tanks the CC uses. A few are pretty much universal, I think, so there should be some. Regulator Arrow, if you want to get a bit frisky, I guess, is one I'm sure of.
As for TAG units, the Ti Tsang and the Owens cover the two ends of the specturm. The Owens is pretty much useless on its own, so its only real role is to find isolated marks for TAG fire (in other factions, it might haul BA, but in the CC even that is denied to it, since they use mag clamps). Conversly, the Ti Tsang is the sort of mech that needs to be in the opponent's face anyway, so it may as well use its TAG while it's there. It definatly gives you some good coverage.