Hi,
I have two Victron Multiplus ESS Systems in the same house (older and new one, different batteries). Each has its own Cerbo and both running in ESS mode with the same Grid Meter. This is working but if Venus OS would have the ability to use one as a master and others as slaves would be cool, because for example sometimes one battery starts to discharge and the other one starts to charge with the energy of the other one. Not efficient. So now I control one by modbus and switch charging on and of controlled by Home Assistant, but native would be way better!? And sure some would buy more Multipluses and Cerbos… 
That’s a big ask. I run 3 ESS on the same meter. I use this Node-Red flow to disable the charger overnight. 2 units are mostly solar soakers for the big one, and may not charge from excess solar if there is none. I have a mix of MPPT and AC-coupled solar.
The flow is in the text file if anyone needs it.
SET CHARGE CURRENT FOR THE DAY.txt (5 KB)