Trying to grow the Ultras group and improving home atmospheres is something I have done to death with the football club over many many years. I could write an entire essay on what works and what's a complete waste of time etc.
I don't have time today to go in depth on here about it but the easiest and best thing you can do for atmosphere is create an unallocated seating section at 10% lower capacity.
The singers can group together, you can naturally grow the singing group as years go on.
If I said we're bringing the Ultras back and need 100 people to "sit" together, we aren't buying 100 tickets in a row or across multiple rows game after game.
If the area behind the goal had this I would be tempted to buy a season ticket in there, however looking at plans and locations for away fans I would be encouraging singers to congregate behind the opposite goal alongside the away fans, identical to Derby. The proximity to away fans will ramp up the atmosphere and would be far more enjoyable than sitting at the opposite end in front of a hotel miles away from the roof.