The mapping of these signals to circuit network channels would actually be an interesting feature because as ssilk pointed out over in that other thread having too many different conditions would turn out way too complex since AND/OR'ing them together inside the Train is really ugly if there's a lot of conditions that have to be met at the same time.
That's where the mapping of these signals would come in handy because then you can offload that condition mess to the Circuit Network, using combinators to do pretty much whatever you want with these properties and then lead the results back in and use "Wait on Circuit Network condition" instead.
That feature would also be a lot easier to expand upon without further convoluting the wait conditions menu inside the train.
Things that could be mapped to a circuit network signal by the trainstop are at least:
- Train Inventory Full/Empty (Could be a 3-state signal with 0 = not empty, but also not full, 1 being full, 2 being empty) (maybe make it a percentage bar alltogether with values ranging from 0=empty to 100=full)
- Train item contents/count obviously to their respective item channels like has been demanded in the past and probably is going to be added in 0.15 anyways
- Amount of Locomotives/Wagons a train has and how many of them are empty/full
Maybe people can come up with additional properties that could be extracted from trains and mapped to circuit network channels by the trainstop... like tagging trains with a unique number Id and so on, which would be nice for Smart Train stuff (I know mods can do it already).
TL;DR: The idea is basically more than just "Send train Item contents to circuit network"... it's about adding the foundation for sending any possible property a train/trainstop can have to the circuit network by mapping them to channels... and using the Circuit Network for doing all the condition stuff instead since it's way more flexible.