another option is a Section 31 infiltration scenario, the team is sponsored by Section 31 and is tasked with infiltrating into whatever organisation you choose.
I have played several 'mercenary' scenarios from Raiders, Renegades and Rogues from LUG, there are plenty of options in that book, the DS-9 sourcebook also discusses non Starfleet teams.
"I will never make excuses for who I am. It is the way I was born. I am a HUNTER. a BONE COLLECTOR."
Wave Man, the term "wave man" is the English translation of 'Ronin' (Japanese word) and literately translates to "wandering person" and in a modern context a WaveMan is one who is socially adrift or a SalaryMan who is between employers.