There are plenty of independent groups and places in SARP, but we still need more. There's Nassau; An independent and law-abiding port controlled by a Oncari Industries, a small-time ship builder. There's Halna and their pirate population, lawless as any place. The Yggdrasil is a ship of salvagers and free people, though their captain has a slight pro-Yamatai government bias. There's also CSEIA, which is a black market research corporation and a private university. They're run by scientists and function mostly as arms dealers. Perhaps take a look at one of those locations/groups before creating your own, it might give you some insight into what galactic politics are right.
However, most nations have no 'elite forces' or need for private militaries, since their own technology is among the best in existence. Only Nepleslia seems to actively use 'G.I. Joe'-style ruff n' stuff infantry forces, but I believe its purely a nationalized army thing with no room for independents. Everyone else seems to use cloak-and-dagger special forces, or starships with mechanized power armor.
I don't think most of the criminal sector will have the money needed for mercenaries, since they have very high upkeep. You may get the occasional mission, but I wouldn't hold out for consistent action. There just doesn't seem to be a market for independent platoon-sized infantry forces, I'm afraid.
And yes, you can submit any item you want. From firearms to robotic arms to sex toys. Whether it gets approved is an entirely different matter, which is left to GMs.