They certainly can do that. Its an unanswered questions, where is Prime Lorca. One theory I have is that the crew being held captive (they killed one of them in front of Lorca) is PRIME Buron crew. And the two ships traded places. I seem to be in the minority with that opinion though lol
But for me, the issue is still similar. If they keep Isaacs as Prime Lorca next season, we still get the wonderful actor. But we dont get the really interesting character. He would be different. One other possibility is that Michael keeps his secret and we get Mirror Lorca forever. But the preview for next week shows Saru addressing the crew saying its no longer Lorca's ship...so I assume she spills the beans to everyone and Lorca is considered a bad guy.
It would be more nuanced if he was a rebel and thus a "good guy" in the Mirror Universe. We'll find out soon enough.