Custom time ranges for availability - an easier way?

We would like to start using Bookings to allow customers to book one-to-one time with our trainers. Often, availability is very specific with varying buffer times between available slots, and therefore we would want to specify the availability ranges. At present this is possible via a drop-down menu, but this is cumbersome when setting up lots of availability slots. 

Would it be possible to allow users to paste in the desired availability, rather than selecting each start and end time from a drop-down menu?