Allow custom waitlist enquiry or a special interest waitlist

I would like guests to add themselves to a waiting list on any given day, at the moment it only works if there are sold out slots on the calendar. I'm wanting them to add on days I'v closed, so if I decide to repon that day in future, I can invite them to book. It could also work on days I have no events, handy for gauging customer interest on days you don't host and see if you get many waiting list requests to look at hosting events on those days as well. So just a more open waitlist option as apposed to being restricted. Maybe this could be something different like an events interest list, or special date request list. We have tried a work around by setting my event time to a smaller time, which then shows the day on the calendar to select under the waiting list option but because there are no time slots available it doesn't allow someone to actually submit the request. So either allow them to submit a request without selecting a timeslot or allow them to chose their own day without it being restricted, or finally to request a special requested booking day on days where there are no events or timeslots.