I am a fan of pirates using well pirate grade material, Wasp's with Stinger Arms, Stinger's with Wasp Legs. Wolverine with Shadow Hawk and Griffin Parts.
The original Scenario Packs also had most mechs having some kind of borked equipment, Gyro or other Critical hits, -n Heat Sinks, the Primary weapon can only fire once every couple of turns, less than a full load of ammo, partial armor due to none being available for repairs.
I would do the same thing for any ASFs, Dropships and Jumpships, Heat Sinks, Armor, Weapons, borked, critical hits applied.
I would also add some negative traits for pilots, if they are any good, give them addiction or psychosis. If they are regular or green, some manner of ner'do'well, PTSD, AWOL, or Criminal Warrants.
But you can also add some flavor, like connected with the Yakuza, or still friends with the Quatermaster from the old Unit, or even House Intel agents. Or even a Dragoon or Comstar operative.