I spoke to the baseboard builder at Warley, who was optimistic that wood supplies had improved to the point where it will be possible to build the layout in the new year.
One issue is how I actually go about laying the track and wiring the layout in light of its position (i.e., on spur shelving around the room at eye level for a standing position and, down the longest edge of the room, above the existing N gauge layout). The issues are: (1) the layout will be high, so laying track will be difficult; (2) the layout will be wide, so reaching the back will be difficult; and (3) the layout will be over the N gauge layout so reaching underneath for wiring will be difficult.
What the person from the baseboard builder suggested was breaking down the layout into modules, laying the track and doing the wiring on these when not mounted to the wall and then fitting these in place.
Below is the track plan showing (in grey) the baseboard join zones (which are wide to reflect the area that needs to be kept clear beneath the baseboards for the joining structures:
As will be seen, there are (unavoidably) a number of places where there are points or crossings which straddle the joins in one way or another. As this will be a permanent layout, it need not be dismantled regularly, so, as the baseboard person said, it may be acceptable simply to align the plain tracks using rail joiners once the boards are all in place. As for the points and crossings, however, how best to do this is more complex. Presumably, what will need to happen is that, at some point during the build process, one board will need to have part of the turnout hanging over the edge, only to be fixed in when lifted into place and secured on the spur bracket. Presumably, except in the case of crossings, the side that is fixed in place will need to be determined by reference to the need for the toe to have a point motor attached to it.
The next complexity is how actually to lift the boards into place. These are likely to be very heavy, and one slip could cause serious damage to the N gauge baseboards below. I may have to get the baseboard builders to come back once the modules are completed just to fit them.
Another question is signals; these are much more delicate than track, and will presumably need to be added afterwards. They are much fewer than point motors, etc., so it may well be possible to do these with the baseboards in place without excessive difficulty.
Thoughts on the practicalities of all this will be appreciated.