From: The temperate climate zone
Please let us group different side's units.
We have multinational task groups out there. Of course I could just enter all units of SNMCMG1 (roughly a dozen units or more)being in a "NATO" side. But this group gets regular replacements of new units, while facing other units exiting the group, probably returning home or towards other tasks.
At present we would then have to delete that exiting "NATO" unit and replace it at the same location with the national unit, being identical of course. Same in the other direction, when getting a replacement merging with the group.
Enabling this feature wouldnt need to check side postures at all. It may then technically possible to enter hostile units in the same group, but I dont think a mission designer would seriously do so, so you could possibly abstain from entering program code for that checking. If you would have the program requiring different sides to share friendly posture to group units of different sides, this probably would restrict mission designing in an unwanted way (with the present amount of different postures). In real life we have german, brazilian and indonesian units in the UNIFIL-MTF. These work together at the coast of Lebanon, but does this imply they are allies all over the world? Rather not.
An alternative could be to have grouping units beginning with friendly stances and also to add a new posture named "ally" that is beyond friendly and a true global effective mutual stance.
Side does not equal nationality. You can put all nations you desire in on group as long as they belong to one side, i.e working together for a common goal like multinational task forces usually are supposed to do. To create allies you just create a different side but with a friendly posture. They will then be allied to your side. I do believe you are describing a problem that does not exist, since this is an operational level simulation.