Nice idea.
Too much work, not interested.
As a suggestion, I can state the idea that came to me when the UFO Hunters-Killers were added. It is somewhat simpler, maybe it will not be so difficult to implement it. The idea was to equalize the capabilities of people and aliens, not only in air combat, but also in ground combat. Now people can attack downed UFOs, and aliens cannot attack people from a downed transport worker. So, the idea was that the Hunter-Killer should have another property - can they sit down after people from a downed transport worker. It makes sense to assign this flag to big Hunters carrying many aliens and terrorist units. Small ones, with a small detachment of aliens, have little chance of winning, so the flag is not assigned to them - they only shoot down planes. So, if the Hunter-Killer knocks down an X-Com transport, then if he can, then he descends after the survivors and lands. At the same time, the soldier scatters around the battlefield (they parachuted with parachutes and did not have time to group themselves), and from their weapons and equipment they only had what had been assigned in advance. There was no equipment window before the fight, but the one that was already assigned was fastened to the uniform or was at hand, so professional soldiers could grab this weapon when leaving the ship. The aliens themselves are partly inside the UFO, partly manage to disperse across the battlefield (as they do now when attacking a stranded UFO). However, many people may be at a disadvantage, surrounded by enemies. The initiative of the first move will be for attacking newcomers, but the X-Com soldiers will have the opportunity to respond to the return fire, as it is now on the first move in a normal battle, only the sides change places. Opportunities to evacuate people do not have - refusal from battle is a recognition of defeat. In case of victory, soldiers can use the help of local allies to return to the base, but lose all trophies (they are picked up by the local army or whoever is there), and their equipment is destroyed, according to the instructions. That is, the return will still not be fast, all equipment is lost, only the battle is added, in which the soldiers have to defend their right to life.
Sorry if it turned out incomprehensible. The text was translated into English with the help of a Google translator.
Update: Yes, probably it is better to clarify right away. I myself do not create fashion, so this was an offer from a player who wants to see diversity in mods, not a modode's proposal. And it is worth realizing it only if there are interested mod creators interested in it. They may somehow complement it, how it will be better suited to them.