I figured out how to spawn a vehicle from a client-side addaction without getting vehicle cleaned by the server cleanup.
You will need a new file in your custom_server.pbo @EpochHive\Addons\custom_server\Init.sqf containing:
"EPOCH_TEMPOBJ_SAVE" addPublicVariableEventHandler{ _veh = (_this select 1); _veh call EPOCH_server_setVToken; _veh setVariable["LASTLOGOUT_EPOCH",1000000000000]; _veh setVariable["LAST_CHECK",1000000000000]; };
Now, from your client where you are creating the vehicle, call this new handler
_vehObj=createVehicle[_vehClass,_position,[],0,"NONE"]; EPOCH_TEMPOBJ_SAVE = _vehObj; publicVariableServer "EPOCH_TEMPOBJ_SAVE";
Now, I do not run stock AH or BattleEye on my server. If you do, you may need to come up with additional filters.
This code works for me. I'm getting vehicles created and they live until restart.