Ok, perfection would be combining your **excellent** booking limits feature with a waitlist.

Like this:
- prospect arrives on landing page, gives first name, email, phone so that I have their contact details whatever happens because I've spent money getting them there
- calendar displays, prospect sees no availability because... I'm so in demand
- prospect gets informed they're on the waitlist and will be contacted
- emails sent to all on waitlist when new spots open up / cancellation

All as configurable as you can make it.

What do you think?

Yours, Matt.