A little feedback from an "experienced" player with Kaiserreich : The game will go out of sync as soon as the game in europe starts, even with only 4 players. More players and will mean more out of sync will occur.
You will need a vocal to sync pause/un-pause at least.
You also need a basic set of rules to prevent "gamey" actions, like DoW on Buthan for IC boost or claiming Danemark in 1938 for UoB (minor countries have a tendency to give provinces claimed, it can be around one or two % but it's enough to make the game go wild)
Never been aware of "our of sync" when playing KR in multiplayer.
But only played with Europeans.
Yes you have. You encountered that numerous times while playing with me and Azzinoth. OOS is when a client player can suddenly no longer interact with the game, whil still present. Everything he does is severely delayed and a prompt rehost is the simplest solution.
Ineffective for what? To tell "Hello, I can't be here at 32nd of August!"?