I either read this idea somewhere or dreamed it up the other day.
All players create two characters with different specilisations.
In downtime between missions the player can switch between characters to represent replacements or misson specialists being attatched from other units in the regiment. For example if one character is injured he can be left to rest and recover at base whilst the player uses his other character.
This way not only do players have a premade replacement guardsman who might have earned some xp already if one of their characters dies, but players can also exerience a more varied game using two different tactical approaches.
We fluffed it out as our platoon having two squads who had to be kept apart due to a number of personal rivalries i.e. If we take jeff rom squad 1, jake from squad 2 will have to stay behind.