One of the difficulties of reviving EDI when easyJet come off the route next month is finding an airline in a position to operate it effectively. As has been said it needs an early morning departure from either EDI or SEN with a second rotation in the evening. Effectively that means using an aircraft based at either EDI or SEN and then utilising that aircraft elsewhere during the day from either airport.
I understand that Cityjet are not interested and Flybe won't want to dilute their upcoming LCY-EDI service so perhaps someone can suggest an airline, with the right size aircraft, which may be suitable. I'm sure SEN are looking hard to find one.