I imagine negotiating to have real football players appear as skins in a war game would be considerably more difficult than using fictional characters played by actors.
Instead, the skins should probably be based on team fans and supporters.
As for the map, rather than using the stadium itself, a large road, plaza, or parking area near the stadium might make more sense.
And if they ever did a special event like the Red Bull challenge, with 64 vs. 64 supporters from rival teams fighting over a single objective under a limited ruleset where everyone could only use blunt melee weapons, I think it would get extremely intense.