Request: Convert an appointment into an invoice and be reminded of unpaid appointments

I've been using Acuity for my real estate photography business since 2020, and love it. I allow customers to reserve without payment (because sessions are often rescheduled/canceled) and I manually charge the card on file once the session is complete. However, every once in a while a card will be declined or have issues, and I have to send an invoice instead. I just discovered that what this does is leave tons of "unpaid" appointments in my calendar history, and I have to cross-reference with my Stripe account to see if they've actually paid or not. It would be incredible to have a third option (alongside "credit card" and "cash" payment options) -- a "send as invoice" option which sends the appointment info to the client as an invoice, and then updates the status of the appointment to "paid" once payment has been made. 

I'd also LOVE the option to be notified if an appointment is still marked as unpaid after X days -- I discovered that I forgot to manually charge the card for several completed photoshoots in 2020/2021, and I'm now out of luck given how long it's been.