Many of us are spending quite a lot of energy trying to figure out what the rules are with respect to local government reorganisation. The thing is, I'm not sure there are any. Jumping straight from manifesto to White Paper means we haven't seen the evolution of thinking. This, combined with implementation needing to start in parallel with the legislation being published, makes it an exercise in parallel realities.
The White Paper has provided guidance and a sense of what Government is after but it's very different from a published set of assessment criteria. Their absence means either guessing what the assessment approach will be and pitching for that or taking ministers at their word and building the best case possible for your place based on your deep knowledge of its needs.