After watching Enterprise season 4 mirror universe episodes, I thought up some possible mixed ideas.
1. I'm the captain of a mercenary vessel transporting cargo to the Gamma quadrant, but upon exiting the wormhole in Bajoran space, we find ourselves in the mirror universe, where we could get into a firefight with some Klingon or Cardassian Alliance warships, find the Rebels or they find us.
2. I'm part of the crew of a federation cargo ship delivering cargo to a secret Federation base in the Gamma quadrant. Our ship sustains some damage, which affects the wormhole, and we find ourselves in the mirror universe, one where the Terran empire never fell. My ship would be captured by a warship, captained by a captain who recently lost his woman in an attack on his life, and I just happen to look and sound exactly like her. The rest of the crew could be killed, all but me, with me being made to take her place, with his crew sworn to secrecy, upon pain of death.
For this one, I would need someone famliar with the mirror universe, who could play a terran empire captain, that one is the one that interests me the most.