It's all there in your Apple ID/purshases settings... there is a big "manage subscriptions" button. Same on the iPhone. Doesn't get easier than this.
- Change your country/region
- Be forced to add a new credit card, regardless of how many times you've done this before
- Attempt to load your subscriptions, and receive a "Cannot Connect" error no matter how many times you try
- Restart your phone because its the only thing that seems to resolve this
- Successfully manage your subscriptions now that they will load
- Repeat the entire process again to get back to your original locale
This...could be easier.
I haven't heard of this. Is it a supported case by Apple?
I think the simpler workaround is to have multiple Apple ID/accounts, one for each country and linked to specific payment options. It still requires signing out and signing in, but it avoids restrictions (IIRC, something like 90 days) and the need to re-update payment information as with the other approach you mentioned. The subscriptions may not work when you're not signed in to the account associated with its country, but this is simpler than following many more steps.
I find it silly that Apple does not even consider switching between two countries as a use case that would apply for quite a number of people (it may be less in percentage terms, but surely a large enough number in absolute terms).
This is obviously not the mainline use case, but to suggest that "no one" does this simply because you do not is obviously naive.