@Dave - I'm not sure this is the solution Thomas was looking for.
I was looking for similar solution some time ago.
The problem with exclusions is, that it works globally on VBR server for all jobs (If I remember well)
The idea is that you maybe can process instance #1 in job #1 with credentials #1, instance #2 is processed in job #2 with credentials #2. This would be somehow a logical concept as every instance is practically a separate installlation of SQL (although all residing on the same VM)
This way you can adress also the request for different retention periods for backups, different schedules,... ( GDPR comes in mind...)
This would be especially useful with AoAG with multiple instances installed where you have a lot of data to be processed.