I'm actually prototyping a similar distributed messaging app using remotestorage.io to try to tackle this issue of profile roaming and persistence. In theory it should allow profiles to live in the cloud (in any backend supported by remotestorage, such as Dropbox, Google Drive, and ofc remotestorage servers) and be sync'd automatically across devices to enable features like roaming profiles and simultaneous logins in a distributed manner.
In practice, however, there is still a number of complications such as the need to secure the data being stored from storage providers (remotestorage itself doesn't offer encryption natively), and coordinating communications between accounts with multiple devices (network endpoints) to minimize network inefficiencies. I'm mostly done with the former and steadily making progress toward the latter, so I feel this could be something to consider for the Tox team as well.
