A rebuttal is a direct, factual answer, claiming that having an RPG was Fasa pushing you to have megagames was not.
I claimed no such thing. I will absolutely claim, however, that an RPG campaign of practically any stripe imaginable calls for a group of typically a GM and 3-6 other players. That's not a "megagame" but I feel I can confidently state that even a "small" RPG group of 3 players and a GM playing OpFor runs headfirst into the issues I described.
BattleTech has
absolutely nearly since its inception promoted games large enough to run into these issues. The difference is that in the 80s and 90s that was just the price you paid to get a game in.
We can do better.
Still unanswered: have you seen *any* other game system pushed as far as BT and still hold up? How many times have you seen 12 people at a single game of any other system? What is it that makes other systems run better at this scale, assuming you've seen it done?
I'm going to be honest here: even though I did directly address this, I really don't care. Please don't interpret that as disrespect, because that is absolutely not the intent. "But can <other thing> do it better, huh?" is not and never will be a compelling argument to not attempt to improve.
If you're unwilling to make an apples-to-apples comparison, I don't see the point in continuing this discussion.
On topic of "But does <other thing> do it better?", perhaps this is for the best.