I was able to finish Battletech last night.
The final mission did, in theory, take extra pilots and mechs. They tell you that you need at least two heavy lances worth of mechs.
This was not correct. You just need 7 mechwarriors and 7 mechs in case you lose 100% of your force while winning the first of two connected missions. I lost zero mechs and zero pilots - I severely outgunned the opposition. Their "assault lance" was much lighter than my lighter-than-usual lance. I skragged them easily.
The final fight was a bit tougher, but only because one enemy mech is a rule-breaking monstrosity. Of course. I trashed it - with some equipment losses (an AC/20++ I'd found) but otherwise . . . a straight fight and I brought my three best pilots and my three best mechs to support the client in her battle. I've had tougher throwaway missions.
Still a very fun game, and I intend to keep playing with my rich-and-successful mech company, and may later start a seperate campaign once I've done a bit more messing around.
Well worth the $10 or so I paid, but I'm glad I didn't spend $40-50 on it. Good game overall, yes, but I'm cheap when it comes to gaming since I'm not a big latest-and-greatest player.