I don’t run any instances, but that does seem potentially like a pretty neat idea.
I am really curious about the unexpected behaviors of your instance members though! What are they doing, just treating it as a general instance and not really engaging with the local theme?
I assumed, by “They are not being as used as I expected/hoped.”, that the OP was implying, "- by the members of said instances". And that the closed-registration bit was part of the proposal, not the existing state of affairs. I didn’t realize their instances were already closed-registration.
Ah, I see. I misread a bit. I thought they were being used differently than expected, not less than expected.