One way to take care of the problem is to use something like the troupe system. Suppose the player group is a referee and four players. Everyone including the referee rolls up three or more characters: a primary, a secondary, and one or more extras. You don't even have to decide which of the three or more is the primary, secondary, or extra until you've rolled up the whole crowd. Run through all of the character connection rules do that they all know each other.
When play begins, if the party has a ship that fits the whole crowd, everyone is aboard, but only the primaries are played regularly. Everyone else collects their shares or salaries, but isn't actively played.
If a primary goes off stage for a while (in jail, left behind for months of intensive training in Zero-Gravity Basket-Weaving, medical low berth awaiting the growth of a new liver for transplant, etc.), the player runs their secondary. If an extra is ideally suited for a specific session (the only one who speaks fluent Oynprith), the player with the least useful primary takes over the extra, even if he or she didn't create that extra. (Primaries and secondaries belong to individual players, but extras belong to the group.)
Occasionally, the referee might have a special adventure aimed at secondaries or extras, to maintain the feeling that they're part of the group.
If the party doesn't have a ship that will fit the whole crowd, limit the group to primaries and a few cool extras.
If a character dies, the player takes over with the secondary, or maybe an extra, which becomes a new primary. If there's significant carnage, everyone rolls another extra, and the connection rules link them together and to the existing characters. If a new player joins temporarily, he or she can pick an extra. If a new player joins permanently, everyone rolls a new extra, and the new player rolls a primary, secondary, and extra, and again the connection rules bring them into the crowd.
The reason for rolling a group of characters when one or more completely new characters are needed is that the connection rules pretty much assume a group already, so they work better for several additions at a time.
This originated with Ars Magica, where the primary was a wizard (magus), the secondary was a substantial non-wizard (possibly with innate magic, but no spells), and extras were termed "grogs". But the idea is nor tied to any system or setting.