Mods can be changed 'on the fly'. I am not sure but with --postexec it might be possible to change the mod file so that the recruitable commanders will be different for one turn at a time. All units/commanders would be available at every fort, though, as long as you are unable to mod sites...
I think the --postexec is only executed in the host-computer, so the game would have to change the mod file of that turn too. I'm not sure if this would work, but wanted to share the idea...
And this mod seems to very interesting.
