Tips for running a open table campaign with 6-7 players?

Hey there,
I'll be running a open table campaign together with 6 friends. We're playing Mothership and I'll be the GM.

Since we're old adult farts and have a busy life, there is no chance that seven people can make 5h in regular intervals. So I thought that players characters can hop in and out of the campaign. We'll be playing when three of the six players have time.

I'd still like to have some narrative cohesion and was wondering if anyone here ran a campaign like that and if there are any tips you have for me, especially logistics of people, characters and narrative.

My initial plan is to split the group in two, have a session 0 with both groups separately, then have the first session with everyone and after that it's open table. I plan it to have it mostly anthology based, so session stand for themselves. But I would also like to have an overarching narrative/plot that develops alongside the players.

Since we're playing a hard sci fi settings, I think it's not to much of a problem to narratively have the group split up (two or three working on a stations engineering, doing a transport job, whatever).

One of my thoughts was that scheduling should require having a clear picture who attend which session two sessions in advance, so that when running a session the player who might be there for this session but not the next, bails out of the group, because of reason X.

Any other tips, gotchas and issues you encountered while running such a campaign?