There are two interesting parts in the post.

One is about all the steps of zero downtime migration. It's widely applicable.

The other is the decision to replace a cloud instance with bare metal. It saves a lot in costs, but also the loss of fast failover and data backups is priced in.

If I were doing this, I would run a hot spare for an extra $200, and switched the primary every few days, to guarantee that both copies work well, and the switchover is easy. It would be a relatively low price for a massive reduction of the risk of a catastrophic failure.

The hot spare switchover idea is good. Another related idea: restore each from backup regularly.