I have spent the last 3 months considering and evaluating many different concepts for my next layout, in both T and N, and have finally settled on the highly original idea of Ribblehead (in T). To try and preemptively reduce the confusion with the two other Ribblehead threads, for the purposes of this forum I am calling mine Blea Moor. Although it will probably end up being called Ribblehead elsewhere.

The detailed design is still in flux, but the overall concept has settled down nicely.
Serious construction is scheduled to start in December.
The top level requirements are:
- a new exhibition layout, aiming for a first public showing in August 2018
- single-handed setup and fully automatic operation
- at least 2 trains in motion in the visible area most of the time
- as large as practicable, given transport and running-at-home constraints
- a narrow thread of railway lost in a large landscape
- no points
- few trees and buildings.
The main design features include:
- the visible area extends from the overbridge just beyond the Blea Moor loops through to the overbridge at the far end of Ribblehead station (2500m straight line or 2800m along the track in real life).
- two block posts (Blea Moor and Ribblehead) for train control, so 2 trains will be moving and up to 4 will be visible most of the time
- the layout will be a double track oval with no points, with half the track behind the backscene. Sidings and loops will be dummies. The Blea Moor loops will be designed for upgrading with working points if a decent product ever eventuates.
- the time period (for track plans, etc.) is not fully defined, but set prior to the line closure attempts, with loops at Blea Moor, double track over the viaduct, and either one single or two staggered platforms at Ribblehead
- built on either 3 or 4 baseboards, 5'-6'6"" x 2', with a total frontage of 16'-18' (final configuration still TBD)
- overall size and configuration as close to the prototype as possible, though probably requiring 10-20% length compression of the non-viaduct sections and curve straightening of the non-viaduct sections
- a curved baseboard design to support the 80 degrees of curvature over this stretch of track (although reduced to around 60 degrees by the compression), with viewing from the inside (east). This maximises the radius of the 180-degree curves at the ends, and allows me to set the layout up in the corner of a room at home for testing.
- minimum curve radius of at least 10" for the 180-degree curves, with negative super-elevation to try and keep long(ish) rakes of 4-wheel wagons on the track
- no gradients. The prototype gradient varies between 1 in 100 on the viaduct to 1 in 300 in the stations, but this will be ignored for simplicity and maximum train lengths.
- the control system will be a further upgrade of Sarum Bridge's, with independent control of each track, more than 3 trains per track, back-EMF feedback and anything else I can think of.
- all (or most) structures 3d printed by me.
A rough preliminary sketch of the design (Google Earth, slightly compressed in GIMP):
Nearly-final CAD shots of arches for the viaduct:
An early work-in-progress CAD shot of a king pier:
More to follow as events progress!