Yeah, you just have to accept that the idea of heirloom mechs hundreds of years old and long, long careers in the cockpit are incompatible with the TT rules. Because BTech is lethal as all get-out.
If you treat each battle as part of a RPG campaign, where you or your opponent can simply agree to a temporary truce, or accept a surrender with a small settlement, without destroying the other 'Mech, you probably wouldn't risk losing your 'Mech once the armor took a few hits, and withdraw to fight another day. Fights to the destruction of one side or the other don't match the earlier fluff text regarding the 3SW and raiding in its aftermath, but the recovery of manufacturing techniques and plans made that the preferable answer in the 4SW. In a pick-up battle with no "tomorrow" to worry about, it's the obvious choice.