lexicons could be updated to be tolerant to use a string format that's tolerant to both at & space uris
but yeah lexicon authors would then have the ability to basically decide if a record is meant for public/permissioned/both
That's sort of where I arrived while figuring out what adding arbitrary lexicons to stratos would look like, the most flexible option was simply denoting some form of attribute that could declare that.
I personally don't think a new URI is even needed as it's addressing at the end of the day which can inherently indicate if it's private. I'm still seeing this as a protocol extension rather than new protocol