I'll go ahead and echo that List seems like the most practical style of character generation. As for my character concept:
I was thinking of playing a Salarian Infiltrator, ex-Special Tasks Group. He was disavowed by the STG after a failed op on [REDACTED] in the [REDACTED] Systems, where he demonstrated high risk tactics and flagrant disregard for [REDACTED] and the chain of command, exposing his team to unnecessary danger and resulting in the [REDACTED] of [REDACTED], a mission critical asset. Most recent surveillance reports show that he works as a mercenary, based out of Omega, taking contracts for ops that official channels can't be seen involved with, involving bounties, corporate sabotage, and internal security. His clients are varied, and include the Hegemony, Systems Alliance, [REDACTED] Group, Citadel [REDACTED], as well as various corporations and private interest groups.