I personally think that for the new station to be served by all "non fast" trains (Ie 4 Thameslink from the GN line, two from Liverpool Street plus the Stansted to Norwich train) at 7 in all should be enough, so not the Kings Cross Cruisers or the Liverpool Street peak fasts.
We all want good connectivity and it's going to be an important station, however this should not be at the expense of losing other benefits like the non stop headline of the Cruisers.
There will be one an hour from Ely, plus it's easy to change there so no issue coming from Lynn or Peterborough. Once EWR comes to the party it will also call, so those as well will be plenty.
On the layout, would two islands really take up more space? Surely the width of two outer platforms would be more than a second island,
The station for instance would need 4 lift/stair sets (rather than 3), and the tracks would have to fan out wider on approach to spread around them. Which means a widened alignment over a longer distance.
The other facet of "user friendliness" is the side platform gives one platform from which the hospital / biomedical campus can be accessed without any level change.
the busway overbridge looks a bit tight but could easily be widened, as for Long Road bridge bigger project would be needed but is well overdue anyway.
The busway bridge (with cycle paths) is only a few years old, and already has to fall relatively sharply to meet Francis Crick avenue.