It could just be a fixed reward that only one unit per faction can win in a given time frame.
Sure you can help each other out, but it'll be on an every other cycle basis. If both of you want the rewards every cycle, you part ways and go separate factions and try to get #1 in your own respective areas.
To ensure that units who are adjacent and can affect each other's results don't work together, the earnings of each faction should be affected by the actions of the other. If 2 factions are fighting over a border, the unit that wins more simply gets more and the unit that loses that exchange gets less by a significant margin. They still both get something, but both of them can't have a full slice of cake each (example, one side invades a neighboring faction and takes some territory, they gain +100 MC while the loser gets a -200 MC penalty).
I'm sure there are a few more details that can be worked out in terms of minimizing the chance of units collaborating.
Edited by Elizander, 28 October 2015 - 01:12 AM.