I would add the Spider, Ostscout, Phoenix Hawk and maybe even the Mongoose and Talon to the list of mechs they might use.
Vehicles might be something like the Nightshade and Ripper VTOL's, Rotunda and Packrat wheeled vee's, Beagle and Gabriel hovercraft, and maybe the Galleon tracked tank. Maybe something like the Manticore heavy tank to provide some more firepower.