Yes, the signalling could be tricky. The shunt disk is pretty standard  as are the position lights, albeit with route indicators; I'm sure that  there must be a wall mounted banner repeater out there somewhere,  however the semaphores will probably need to be completely bespoke. The  idea is that they are replica McKenzie and Holland semaphores with a few  modern adjustments. The originals only had a red spectacle plate and  therefore showed a red light for on and white for off when there was no  spectacle plate in front of the light. The replicas have LEDs which go  green when the signal is pulled off. Having qualified and worked  Porthmadog Box a couple of times I can't see how it would be possible to  replicate the scheme exactly in Trainz (I've had a go myself), but with  the new version of Trainz adding an interlocking element the situation  may be able to improve.