Power BI Gateway Query

Hi All, 

We have a power bi gateway that we need to upgrade however a contractor did not record the recovery key. 

As a result we are opting to setup a new power bi gateway on-prem to replace the old one so we can record the key properly this time and then move the workload over to the new gateway giving us a good path moving forward. 

My query is our old gateway is quite a few versions behind latest, ideally we would like to build a new gateway on a new server with the latest version (so takes care of the upgrade at deployment), then connect the data sources before moving the reporting/config over to the gateway in a phased approach bit by bit to avoid any interruption to the business. 

Is this a supported scenario, from reading microsoft articles they state the gateway versions should be kept aligned to prevent issues or failures due to disparity between versions and capabilities however the migration of the workload may take some time with different teams to achieve.

The workload would not run simultaneously through both gateways in that we would disable on one and move to the other bit by bit. 

Thanks. 

Lee