I'm fully aware of why they will be stopping at Cambourne!
You say "move-outer-ers", what about the people who have already been forced out (who are living in Great Gransden, Potton, Gamlingay, Biggleswade) ?
They can access EWR at Tempsford or Cambourne.
As you correctly say "If you add stops to EWR itself it becomes less effective at serving the longer flows". But by not serving the shorter flows EWR is/going to stoke up a lot of NIMBYsm, because those NIMBY's won't get any benefit from EWR!!
But they do get reduced road congestion.
As I see it, EWR will only be a benefit to people living in Cambourne or who haven't moved into the area yet. It does very little for the people who already live in the surrounding village's (and btw, have you ever tried cycling from Cambridge to Madingley?). Yes some villagers can be able to cycle in, but contrary to what some people think, Cambridge and the surrounding area is not 100% flat !
Yes, transport planning for future schemes is not about current users - it is about the future users who don't exist yet.
— although “no mow May”[1] is good for wildflowers (and thus insects, and thus birds, etc.) 
