The better solution is to link verified phone numbers in one account. You would need access to both numbers simultaneously of course. However since this is non

The better solution is to link verified phone numbers in one account. You would need access to both numbers simultaneously of course. However since this is non-trivial to implement as it requires indirection wherever authentication is performed or identity is asserted, requiring fundamental architectural change for most platforms, the engineering cost vs marketing benefit applies. So the priority level “MUST” is questionable since almost no one has this problem. It is more likely that the solution will be an ever increasing number of cell companies will have agreements for international roaming.