BP-Group-Calendar feature req - reg interest/book

Ultimately it would be great to have an end-to-end booking system associated with events in the calendar, but I appreciate that's rather ambitious and probably a separate plugin.

However, would an 'express an interest' or 'I'd like to attend' feature be possible? It would also be fantastic if there was a configurable limit for each event, i.e. 40 places, and this could be reported with a current count of those 'booking' a place.