The original proposal referred to in this question is the proposal submitted by Adur District Council, Arun District Council, Chichester District Council, Crawley Borough Council, Horsham District Council, Mid-Sussex District Council and Worthing Borough Council for 2 unitary councils in West Sussex.
You can find the proposal here: Shaping West Sussex | SnapSea
The criteria referred to in this question were set out in the invitation letter sent to councils in East Sussex and Brighton and Hove on 5 Febraury 2025.
You can see this letter here: Letter: West Sussex - GOV.UK