The Highlander is....complicated. Lets say what we know: The mech is beign produced in Son Hoa (i think), an independant ex-LC planet, but it still have a kind of deal with StarCorp to keep providing for the LC. The y produce the -694, -734 & -738 variants. Knowing StarCorps, we can assume they sell to almost anyone. Now, in FM: 3085 the MH RAT did no have the Highlander in any of its variant, but the -732 version appears in the Periphery RAT in FM:3145, from wich the MH roll its mechs. Also MUL shows that the MH is the only Periphery user of the -732 and -732b, beign Mercenaries, IS General and IS Clan General the other users for both. The mech itself is not too hightech, with the only SL-tech items beign the FFA w/CASE, Artemis IV, DHS and the GR. In the tech level side, for a nation capable of making FFA w/CASE and Arrow IV, i dont see it out of its reach. But knowing the universe, it could be the refit of old -732 or even introtech -733.
The Brigand is nother beast. We know that the pirates in the Pirate Cluster basically build it from contraband parts, and the ones in Tortuga made some kind of sme-manual assembly line for it. We know that the MH produce the Commando, so they share engine, and for the DA era neither Endo-Steel, nor ER or Pulse lasers were exotic techs. I can see TechWizards from Baccalieu making them in their workshops.