Long term issue: Multiplayer loading of load out and wings is inflexible and hackish

In reply to:

I just had an idea. What if, instead of modifying the *save* code, the *load* code was modified? In other words, load the wings as specified in the mission file, and then load any undefined wings. This change would be implemented at the mission file parse level, so it wouldn't need to mess with the design of multi loadouts.

This would have the advantages of a) simplifying the save code, b) avoiding the need to make the change in both FRED and qtFRED, and c) keeping compatibility with existing missions.

_Originally posted by @Goober5000 in https://github.com/scp-fs2open/fs2open.github.com/issues/2892#issuecomment-727599478_

Loading multiplayer loadouts needs some fundamental changes if we are ever going to change the maximum number of players in multiplayer modes or remove some of the more hackish elements.