I don't think we need a "remember when" opening. I think we could give clues, like the voice-overs they used to do at the beginning of the shows. "The Enterprise is on it's way to Farpoint Station" etc. The uniforms would also give you an idea of the time period as well.
One idea I have had is Sisco meeting with Picard. I would like to see Sisco get over his anger toward Picard for Wolf 359. Sisco has gone through a lot as Captain and Emissary. Maybe now he will understand that Picard was a victim.
I would like to see a Data & Geordi story set pre-Nemesis. it could be as simple as them talking in Data's quarters about what happened in First Contact. I doubt you could get Spiner to do it though.
You could have a Riker & Troi scene where he tells her he has finally decided to accept promotion and take command of Titan.
You could have a Picard & Janeway scene where they discuss their encounters with the Borg.
There could be a Picard & Crusher wedding or proposal or show them with a child already having been married. They could talk about how much longer they want to stay on a starship.
The stories don't have to be that complicated. The idea is to see our old favorites again, so I would want the stories to be character driven. If you just bring them back and have another special effects driven story you would miss out on the opportunity to get to spend time learning what happened in one of the "gaps."