Rolling Upgrades SWITCHOVER with Maintenance Option

When performing Rolling Upgrades to Server, I start by upgrading my replicas one at a time. Once all replicas (B&C) are on a new version and the primary (A) is the only server left on an old version, I issue a "SWITCHOVER" Command to promote a newly upgraded replica (B) and the old version primary (A) is automatically made a replica of B.

HOWEVER, this making older version A in a replica of new version B is BAD and can break replication or have all sorts of unsupported bugs.

I need an option in SWITCHOVER to NOT make the current primary A a replica. I need to be able to Switchover to B and put A directly into a standby maintenance mode until upgrades are complete.