This feels sooo wrong. And if I do not care about MP and just try to play campaign/career am I to buy one because I never see one at all? At least when fighting Capellans, there should be a good chance to see some. They have a nice chassis in the game but no sir, you can't have it because balancing. That thing is slow as heck and as a light does not have that much armor. OTOH...If I get an early Enforcer or refit my stock Black Jack in campaign with an AC10 from start...this is better? *shakes head*
Actually, in the campaign, you'll find that you're pretty much on training wheels until you get the Argo, meaning even though you start with 'mechs like the Blackjack, you'll struggle to actually get heavier weapons in the early game. It's a kind of stealth tutorial and something like it was inevitable in a game as complex as Battletech.
Other people know more about how OpFor composition is coded in the game, so I don't know if there is any faction weighting at the moment, but it's not something I'd worry too heavily about at this moment: it's an issue which has been raised on these forums (and HBS really *do* listen to what we say here) and it's definitely on the wishlist of features going forward. As soon as it makes sense and doesn't impact other parts of the game that are at least as important, HBS will almost certainly deliver faction weighting at some point down the line, and rest assured there are Urbie fans among devs, so it's worth being patient.
The humble trashcan *will* have its day.