I doubt very much that the 501st will allow any of the in-game costumes to be formal status. It is such a huge process to get any new costumes approved, that even if they did, it will take close to a year before they become approved costumes. You'd be better off getting yourself an approved costume first and then having one of the in-game costumes as an informal/unsanctioned costume.
Seriously, the legion has one AT-RT (mini chicken walker from ep III), and it took that guy like 9 months to get his costume approved within the legion.
The costume has to be in the Legion CRL (costume resource library). If it isn't on the list, it is not an approvable costume. To get it on the list, the costumer needs to provide his/her 3 points of reference, high resolution photos of said costume (in every detail), and a CRL write-up to submit to the garrison membership liaison. The GML submits that to the Legion Member Officer, who, in turn, presents it to the Legion Council for approval.
I, personally, think the process is extreme. Realistically, I think the various membership officers should be the ones to make decisions on new costumes, since they are the ones who are judging costumes. It seems a lot of red-tape could be avoided and approvals for new costumes could take far less time.
But that is just me, and that is the current process.
-Bill
