You should go for it. There are a couple of things to note:
1. Being that this is a not yet Legion-approved costume, you would submit it to your local GML who would then submit it to the Legion Membership Officer. It will then be subject to additional scrutiny as every detail must be perfect for new to the Legion costumes.
2. Having said that, you will have to make sure that everything matches supremely well to your reference photos. For example, the pockets on the jumpsuit would have to have the chevron flaps, etc.
3. If you decide to work on this costume, keep a build thread here at Spec Ops, and we can construct a proper CRL along with the costume. That can really help your chances of getting approved.
Make sense?
Being that the jumpsuit is green, would you be constructing it yourself? I am not aware of anyone who currently makes an Imperial jumpsuit in that shade.
Todd