what might be interesting is if you sold older items as well (bear with me) vintage books eg flight briefing for pilots and signed biographies etc. as well as some rarer items to bring a bit more interest ltd edition prints/signed, rare watches I can go on - thats just my idea anyways
Think of the Tiso outdoor experience in Glasgow just as the previous post says a testing booth for headsets, you could have a booth to test jackets for both aviation and marine (if you thought about that route).
my ideas may seem crazy but maybe there is something in there that can be of some use.