The Enclave's motivations aren't entirely the same, I've tweaked them a bit. However, even a lower ranking soldier, (that is what I assume would have the most access to the wasteland at this point) would comparatively, to the five other characters currently roleplaying as vault dwellers, be a god capable of killing them all at this point in the game, potentially without suffering a scratch. Power armor in this roleplay is much better than it is in the actual game of Fallout 3, and Enclave power armor, is better than almost all the power armor in the game. If you insist upon a character like that, I can oblige you, on the condition that they're a really thought out character and have less S.P.E.C.I.A.L. starting stats than everyone else.
Like I guess I can give you a freebie hint. The Enclave is joinable in this roleplay so long as you're a vault dweller unless you possess truly exceptional abilities. You could join the Enclave later on.