Hi @Greg Booth ,
It is fine to deploy changes you list above:
- It's ok to generate a new key. As SharePoint doesn't store the key, if you lost the old one, just generate a new key.
- If you don't want to migrate the mysite, you can do this. And you can set up new my sites for users after migration.
- it's OK. When encountering missing feature issue during migration, it is recommended to de-activate & Un-install the faulty/missing feature.
- It's up to you and generally there is no risk.
- No risk.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.