BIackboard systems are powerful emergent systems.

Swarms of relatively dumb little agents all emergently collaborating on a shared work space.

Emergently accreting complex answers to problems.

The power of the blackboard model is a diverse set of simple agents on a fully shared blackboard.

If you don't have a shared blackboard that all of the agents can see then it doesn't work.

If sharing the blackboard is scary then you'll preclude most of the possibility space.

You'll either get far fewer agents (you have to trust the agent, a high bar to clear)

Or you'll get sharded blackboards, which allow only limited snapshots of the problem.

The same origin model fundamentally curtails the possibility of a blackboard AI system.