The bluetooth peripheral list in settings and system tray becomes available if any bluetooth adaper is enabled. However, if there are multiple adapters and the user clicks on the connect button on a peripheral paired with an adapter that’s currenly disabled unclear error messages are shown and it doesn’t connect.
I suggest in that case the adapter could simply be turned on. Better yet, if a bluetooth adapter has returned any error when trying to connect a device and it doesn’t have other live connections than the one currently trying to connect it could be automatically restarted.
This is something that should be brought up in the bug tracker, as a bug.
Feature requests can also be filed there. I’d suggest to file a regular bug for the problem above, and another bug with the “WISHLIST” severity (this is used for feature requests), describing your idea. Maybe pop a link to the bug in there as well, since they are somehow connected.