I always liked the speculation that for the episode Second Chances with Tom Riker, the writers considered sending Will on his way in a new command and leaving Tom around as a Lt Cmdr. and rekindling his relationship with Deanna. This would create a whole new dynamic with the same actors. Building off of that, I would probably pull in a new XO not from within. Someone very different from Will Riker yet still a very strong leader.
I always liked this idea, myself. I'd really like to have seen it happen. I'd liked to have seen a female first officer; someone who was a strong leader, comfortable in her abilities and not a bitch. Someone likeable.
I hear what you say about Geordi, too. The little time he was on-screen in the films he really impressed me in a way that he never seemed to do during the series. I think he would make a good first officer, too.