I thought it was for the same reason female partisans were removed, if the Medic model ends up crewing the gun there's no female voice lines.
The female partisans had animation issues with team weapons. The Commissar and Sturmofficer don't have these issues afaik. Good point about the Medic.
Afaik the sturmofficer's aura can be partially reactivated via their bulletin, I wonder what would happen if multiple team weapons recrewed with sturmofficer would gather. Would the bonuses stack?
I think the default implementation will stack, but that can be disabled. Are you sure about that bulletin? That is a serious bug.