roaming providers will be able to apply a 'fair use policy' to prevent abusive use of roaming. This would include using roaming services for purposes other than periodic travel
So very much a partial solution. In particular, it's no good for someone who moves long-term or, say, someone studying in another country. Simply changing phone numbers with a bunch of services is a serious pain in the ass even if they all consider the new number acceptable.
As an American currently living in Germany, I've run in to this kind of problem myself. My mobile banking app, for example wants to send an SMS for verification because it thinks connecting from an non-US IP address is suspicious, but I can't give it a non-US phone number to do that with. Providing a different option for 2FA would be a big help.
Having important services tied to a phone number, which remains relatively tied to a country is problematic in the modern world even for people who aren't especially "outcast".