MachinePool platform is currently immutable and any changes made to MachinePool.platform are blocked by a validating webhook.

The MCO does not support updating existing machines when platform details are changed in a MachineSet and consequently Hive does not support making such changes to MachinePool platform. 

The recommended workaround when platform details must be changed is to replace the MachinePool by creating an adjacent MachinePool with the desired configuration.

1. Create replacement MachinePool with desired configuration with replicas = 0.
2. Scale down old MachinePool while scaling up the replacement MachinePool.

MachineSet platform details are mutable and Hive could potentially sync changes made to MachinePool platform to the underlying MachineSet but nothing will update the existing machines to have the new settings.

Possible changes that could be made in Hive to support editing MachinePool platform:

1. Allow editing MachinePool platform when a feature gate annotation has been enabled for the MachinePool. Changes made to platform are synced to the MachineSet on the remote cluster but it is up to the administrator making the change to recreate machines belonging to the MachineSet.
2. Use a similar feature gate annotation as suggested in 1 but replace the underlying machines in a rolling fashion. This will be a complex and possibly disruptive operation depending on the implementation.