Re-reading the 2015 screening opinion, I don't think it's talking about the woodland we've been assuming (i.e. the woodland behind The Burger Kitchen/Funk'n'Fly). Whilst there isn't a map included with the opinion, from the description of the site and the few facts that are given, it would suggest that it's roughly speaking talking about this site surrounding Nemesis:
Things we know from the screening opinion:
- The development site is around 1.7 hectares (the purple area is roughly this size)
- A grid reference of SK 079 433 is given (which, depending on how you read it, either represents the red pin by The Blade, or this is the bottom left corner of the grid square referenced)
- The site is 75m from the Prospect Tower (i.e. the site includes either The Edge Games or Skyride Station)
- The site is only visible outside the park from the South Side of the Churnet Valley, and is less visible than Air, Nemesis, the Hotels and Skyride cables over the garden
- The proposed ride had a high point of 202.5 AOD (above sea level), and the maximum height of the track would be 14.5m from the existing ground levels. The high point is compared to Nemesis, which it states is 'nearby' and has a high point of 202.62.
- The proposed ride would require the removal of approximately 100 tree, most of which would be classed as U or C, but two would be in category A (high quality) and 25 in category B (moderate quality).
- In the conclusion, the opinion states: 'It is considered that the development would not fundamentally alter the existing landscape character of the site and its immediate surroundings.' But they also note that 'at its northern end would allow the 'developed theme park character' to spread slightly further than existing into the currently non-accessed early mature woodland screening.'
That last point would strongly suggest that the opinion is considering the site currently occupied by Nemesis' extended queue line. Not least because it is the only 'early mature woodland' to the North of The Blade site. This site is already part of the "developed theme park character" because it has rides on three sides of it and a queue line running through it. The description of the trees being lost would also fit this area way better than the woodland to the South or East of the site, since most of the trees up there have only grown in since Nemesis was built.
You can also work out that the high point of the proposed ride would have to be within the dark purple outline. Give the maximum height of the track is 14.5m, but the high point of the ride is 202.5m, this means that the high point must be built on ground at least 188m AOD, the outlined area is the only area at this end of Forbidden Valley with land that is high enough to allow this. For reference, the path of the extended queue line after it turns sharp right is at a height of around 188m.
So, yeah. I'm not sure the 2015 screening opinion really tell us anything relating to cross valley coaster or a ride anywhere very near the valley, but on the other hand might be of interest when it comes to SW9 speculation, as it is clearly a different site the park have recently considered for a big ride, and not one that often comes up in discussion.