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.