What I could see for this is a minimal / modern exterior, emulating an airport terminal. The open glass atrium seems to fit well with this. The large arc structure I speculate will show an animated logo of some kind. The interior of the building would see pre shows themed around the idea of a unique flight taking in the sights of the United Kingdom.
The ride experience would be broadly similar to Soarin, but with the dynamic motion that is achieved by FotSL (I expect they’ll use this ride system as it’s proven by Merlin). There’s a lot to cover here, but certainly I’d expect a mix of cityscape, landscape, and monuments such as Stonehenge and Big Ben to make appearances. The finale would take place flying over Alton Towers during fireworks, and then “arriving” back at the attraction itself.
The building could well have space for a small exit shop, this could be an arrival lounge / Duty Free set up to continue the theme. A British Airways sponsorship would add much needed gravitas and class
I wouldn’t hate it