I guess it is the place to propose features, so here I go.
But I have to say that I am french, so pardon me if my english is not perfect.
I think the field operations system is a good idea. It adds more interraction on the geoscape level, and gives more strategic possibilities.
One cool feature could be added to this system. If hunted, field agents could be not always killed by aliens, but also kidnapped. Then, agents could (or not) evade and come back to ATLAS base, but there would have a chance they would have been brainwashed by aliens (damn).
The effect could be that during a mission, the soldier could rejoin ennemy side.
Imagine it's your Rambo that have been kidnapped, then he returns, claiming that he escaped to alien jails and torture chambers. you're quite suspicious, but it's your best soldier and you lack of manpower. So you send him on mission. You keep an eye on him, fearing he has been brainwashed, but he kills aliens, you success the mission, and everything seems ok. A few missions later, you are breakthroughing (guess this word exists) in an alien ship. Your shields soldiers enter, fallowed by your Rambo and his massive shotgun. Sadly, it is this time he decides to betray you, and when the ennemy turn starts, he becomes hostile and kill one of your shield soldier (thanks). Then a sebillian charges in and unloads his massive weapon, wounding badly an other of your men. It will leave no choice but to kill the traitor (ultimately, we could imagine capturing him and unbrainwashing him, but it makes treasons system less severe).
But it could be a real evasion too, and nothing will never happen. Your Rambo would still be a proud soldier of the Xenonauts
An other possibility would be to send a brainwashed soldier on field operation. Then, a major event could happen, like his deffection and a major relation loss in the region.
Finally, with this system, why not add a scenarised mission where you would have to confront and kill a full squad of your former soldiers that have been abducted, and that did not escape, with there actual skills, and top tier equipement (ouch).
It would be emotionnaly shocking to the player to have to fight and kill his former men, and it's in the thematic of X-2, with aliens prefering using humans to self destruct themselves.
So, it 's just a little proposition, hope you liked it ^^
