Okay....that falls into a very very old question, who starts first when in turn based PvP?
Simple answer would be based on agility stat, but this is WRONG because you need to also consider level difference, high level player will simply crush you in one turn.
How about limit the level difference? like only +/-3 level? That would also be pretty off because different build could have a very different outcome in a PvP situation, ie. I can push high agility and intelligence, so I can start first and cast a disable spell, and finish you off. There is probably no way around that, and it will become stat/gear check to determine who win, not really skill/strategy based.
How XCOM can do online match is because you allocate your unit/position by a fixed resource number. You are not limited to 1 player vs another from the get go( and usually have to initiate PvP in close proximity.)
So a proper implementation would be sort of like how XCOM does it, but in a mod like DLC that gives both side the ability to determine how many units, what kind of equipment/ability, and a properly designed map to let player duel their strategy out, like how all table top games do.
1 vs 1 turn based PvP is very boring and useless, since reflex/cool down management/movement are all out of equation in this type of match.
In short, I agree what Stabbey said, they should do what they campaign for, not spend time on this unmentioned feature, for a good review just show how flexible and user friendly mod tool/editor is would be enough. If editor done properly, this could be a very fun table top game emulator for fantasy themed games. ( where you get to blame computer RNG, instead of your bad luck rolling dices.)
