Well, Aux to Struct 3 is only available on the Exchange, anyway. I guess the problem would be trying to get EPtS3...
"Don't let them promote you. Don't let them transfer you. Don't let them do anything that takes you off the bridge of that ship, because while you're there... you can make a difference." - James T. Kirk
They should let players train abilities to inactive BOffs. It would be simple to buy a common engi BOff and train it Engineering Team 3 and then trade him to a friend so they can sacrifice it to give their liberated borg BO Engineering Team 3.
This way there is no screwing around with changing BOffs back and forth from active to inactive duty, and any unforeseeable problems that might result from that.