My choice would be 16:9 with minimal cropping. There are a few ways it could be done - CG to remove the lights and stands at the edge of shots, CG inserts to extend the frame where necessary, new SF shots (not too hard with extending the starscape background for space shots), subtly stretching the edges of shots and as a last resort, cropping.
Some of this would be expensive, but as digital tech gets cheaper it will become more viable.
You realize to do CGI stuff would take a lot of time, work and money to do right and even then it'll be limited in what it can accomplish. CGI isn't magic, it's a process that has limitations just like any other effects technique.
And it would, again, change the look and feel of the scene. This may seem like something but it could have big impacts on scenes in there series where a certain look or "feel" was achieved by being shot for 4:3 now being shot for 16:9.
The show was originally produced, shot, directed and presented for 4:3 viewing. That's how it is MEANT to be seen. That is how the original directors want you to see it. Stop trying to change that. I know we're not talking about fine film here or anything, by why not also complain about and demand cinematic classics like Casablanca use CGI or whatever else to make them 16:9? I mean, I need to fill my TV so who cares what it'll look like. Black bars! The scourge of TV-viewing. And colorize it too!
No. 4:3 is the Original Aspect Ratio of the show and it should be maintained.