We're working on a Stripe integration (see https://github.com/timekit-io/booking-js/issues/20), but you could actually add it yourself with the callbacks. Check out the docs on Github or ping me on Intercom on the page if you need some guidance
Yeah or one could just put the Stripe paywall in front of it. Like imagine a nail salon or hairdresser or whatever using this on their website - Have them pay Stripe first, then upon successful charge they are redirected to your booking.js thing. Very cool.
Make a payment to see "we are fully booked till next year"? I think using callbacks to trigger stripe's checkout.js is not that hard, unless you hate your users.