Bluetooth mesh toggle OnOff server model state by multiple clients

I got the following setup:

nRF52840 - GenOnOffClient (Light Switch Sample) Publish to Group 0xC001 

nRF52840 - GenOnOffClient (Light Switch Sample) Publish to Group 0xC001

nRF52840 - GenOnOffServer (Light Sample) Subscribed to Group 0xC001

However as the sample is sending a unacknowledged set message to the group-Adress (not unicast), there is no status message from the Server. This is causing the two clients to get out of sync and therefore be unable to correctly toggle the state of the server. 

To solve it I considered the following options:

- Each client is requesting the status of the publish address before toggeling (causing latency for user -> not acceptabel)

- Each client contains an extra ServerModel to store the state of the toggeling light (not ideal as the switch should work battery driven and therefore is not always able to follow the state)

- Create a vendor model with a toggle command (if multiple lights get out of sync they wil just invert its state -> lights are not synced)

Is there a better solution or is it not foreseen to toggle light groups with the GenOnOff model. 

Thanks a lot for your help

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