Trek actors who could have been in other roles...

[Tim Thomason]

Realistically, yes, but Visitor believed (and probably believes) she could do both. And if it were simply a matter of having the energy to do so, I think Visitor could have done both roles.

Yeah, I meant logistically you can't have one actor spread across two 22-episode seasons, being produced at the same time, usually with overlapping schedules. Kira (most likely) would have to be drastically cut back in appearances and storylines to accomodate Visitor's starring role across the backlot.

Bajor joining the Federation in S2 would have been bizarrely fast for my money, and essentially closed one of the major plot arcs of the series ("is Bajor ready/willing to join the Federation?"). Especially if you had the The Circle arc at the beginning of the season it would have been even worse, because that arc did such a great job of establishing how much Bajor was still struggling to find itself post-Occupation.

Yeah, on second thought, it could maybe be that she's commissioned as a prelude to membership, but then it could still fall through after she disappears.

Or perhaps they could just shuck her off into the Maquis, and then have her take command after the death of Starfleet Captain Cavit in Episode 1.

 

[Bad Thoughts]

Yeah, I meant logistically you can't have one actor spread across two 22-episode seasons, being produced at the same time, usually with overlapping schedules. Kira (most likely) would have to be drastically cut back in appearances and storylines to accomodate Visitor's starring role across the backlot.

Actually, you could, but it would mean imposing discipline on the production that no one was accustomed to and, I would suspect, most would resist. Star Trek was notorious calling people in early and dismissing them late, but the actors spent a lot of time doing nothing. Filming took place all in the same studios in Los Angeles, and both series shared behind the camera talent. Having Visitor on both shows would have meant coordination between writers, makeup artists, schedulers, and directors. Considering how many toes that would be stepped on, it would have never happened.

 

[Captain Clark Terrell]

Among guest actors, Eric Pierpoint auditioned for several “captain” roles and was eventually given the role of Captain Sanders of the Malinche as a consolation prize.

 

[diankra]

I think I read recently that Alexander Siddig auditioned for Sisko as well?

Take a moment to imagine him as Sisko and Avery Brooks as Bashir...

Not quite: the producers had seen and liked Sid in a Lawrence of Arabia tv movie and asked him to audition for Sisko, not realising he'd been wearing age make-up in that role.
When he turned out to be 15 years younger than they'd expected, they got him to audition for the doctor instead, and rewrote the character slightly to suit him.