FortiManager Cloud : modify the WAN interface of a FortiGate with only 1 internet connection

Hello,

I'd like to move the WAN connection from WAN2 to WAN1 on some FortiGates managed by a FortiManager, just so the physical installation is the same on all gates.

While I am aware that this will bring an outage, and that's OK as long as it is planned, I want to make sure that when the cable is connect to WAN1, internet traffic goes out as it should.

So, ideally, I would prepare the following configuration on FortiManager:

1. deconfigure IP of WAN2 (which is actually used as internet connection)
2. reconfigure IP of WAN1 with the old IP of WAN2
3. modify the gateway in SD-WAN

BUT, logically, if you do step 1 above, connectivity of the FortiGate is lost, so, my question:

Will the above configurations be fully loaded on the FortiGate, before getting fully applied, or will the each step be done one by one by the FortiManager, connectivity lost after step 1 and my install fail, requiring an on-site intervention of a FortiGate administrator?

If it would be the first situation (configuration completely sent to FortiGate and locally applied, before losing connection), I can just ask a local user to reconnect cable from WAN2 to WAN1.

If it would be the 2nd situation, I think I have no other choice than do the change locally, without FortiManager?

Or is there another way?

Thanks in advance!