I do not think that the "Use default settings" to change fixed to random would drop anyone (a widely known fact, except when it comes to lambhax I guess, is that the hosts machine dictates who gets what position, its not something that is synced from every players machine such as a units level, cost, etc). That is likely your best option because as I've said many times before, these types of changes REQUIRE every player to be using the same version of war2 and that has never been the case with combat and I dont expect it to be the case for a long time coming, if at all. Map editors ALREADY allow this and there are plenty of maps that already have units costs modified. There really is no need to be messing with these stats in the game itself. There are better outlets for that (map editor and wargus).
The "Use default settings" to be changed from fixed to random would be a great modification although being able to enable/disable it with a hotkey during game creation would be needed since quite a few maps actually require fixed order AND map defaults (such as friends type maps).