I'm not here to talk about the troubles of last booking session but to give my suggest.
I hope that my bad english is enough to explain my idea.
I suggest to change EuroFurence registration form, NOT Estrel or other hotel booking engine!
Why? It's simple, we are about 2000 attendee for EF23, but we don't need a single room for each one, but about one for 2 people, one for 3 people and one for 4 people, but every attendee can book a room, and that make a trouble like more people trying to books same rooms and a big DDOS of a lot of people that tries to books a room before it finish!
My 2 cents are: Add in EF registration form the registration ID of roommate and who can book the room, only the choice one can book the room because he receive an EF coupon code for the booking, by mail or on the ef panel, with that code he can access, when he want after you accepted him, to the EF days in the booking engine and book the room for 2, 3 or 4 people.
If the choice one can't book the room, just he can give the coupon code and demand to book to another roommate.
The coupon code can be used only one time, if you don't have coupon code you can't book at Estrel, there are only a specific number of coupon code (one for each room that can be booked for EF), when there are no more coupon code, no one can recive another coupon code, if a coupon code isn't used for X days (1 week or the end of january) it will expire and a new coupon code will be ready to be assigned to next one in queue.
That's a way to try to solve "the booking gate", or just use a booking engine hosted on more strong and fast cloud computing system