The only time race, gender or anything like that matters is in the Scenario Hall in the RPG Centre -> Scenario Hall area. If you are roleplaying anywhere else then your characters race is never enforced. If you want a race to be added to the Combine then you are free to suggest it in the Race Suggestions area, assuming you follow the rules there and its an actual Star Wars race.
There's a difference between "never enforced" and "you should totally do it." If you intend your RP to be SWC-Canon, then RP your existing Darkness race, with their existing Darkness Stats and abilities. Your character is what they are.
The 'not enforced elsewhere' is best interpreted as that we don't bother trying to police RP most of the time, and certainly not when it's on other sites (White Scenarios excepted), so have fun RPing as another race if you like, but until and unless that race becomes your character's Darkness race, you aren't RPing the same character.
Appearance is a totally other ball of wax. There are countless RPers who insist that their Amani character looks like a human model. It is poor RP in my opinion, but as long as they are playing their Darkness Race with an IC explanation for why they look the way they do, it's fine, their bit of barbie-fun doesn't hurt us too much.
Abilities are the most problematic, since people will often pick a race for its advantages - which advantages are most likely the result of some novellist's need for a narrative hook, and not at all based on balance and tradeoffs. This is why the Darkness abilities are far more important to adhere to than the cosmetic appearance.
Thing is, most people on SWC barely care about legit RP anymore. They'll take the race that gives them the best benefits for their job, then RP as an attractive human(Or any other race they so desire). The way most people can get away with that is by making their profile private, so while you think they look like a sexy human woman, in reality they are a beaver in a human skin suit. There is over 2,000 active members on this site, so mods can't spend all day making sure everyone is RP'ing as the race they are in darkness.
If you care about SWC being a game with rules and story, be the race you are and just wait till the race you want is discovered(Also, try suggesting it if it hasn't been already; like Dol said). If you just see this as a typical game, then by all means use your workarounds to do what you want. Min-Max, RP as a race you aren't, smoke some deathsticks, get drunk... Just don't get mad when people call you out on it. This game used to be an RP thing, and people get upset when things change.