I think there is still something wrong with the way anims are synced. One can bug the thing by updating actors while simulation is running, but I believe that's ok. For some reason though and while anims are perfectly synced in the blendfile, I couldn't sync the onager's anims perfectly in the game.

Is there any documentation about the usage of ids ? and more generally anything all those actor format changes ?

I'm kinda lost with all of those.