Is there a way to simply disable the Merc mod or other components one at a time to figure out where the OOS error is? I, too, was interested in playing this mod on LAN, but got an OOS error early in which pretty much kills enthusiasm.
Edit: I decided to try setting
Game Turn Mercenary Creation = false
in the Mercenaries Mod Config.ini to see if it has an impact(false means mercs are created on player turn start rather than game turn start). Only time will tell.