If you wait for somebody else to build your favourite route, then I'm afraid you're in for a very, very long wait.
Firstly, by my reckoning, there are probably no more than a couple of dozen active route developers in the whole world. Here in the UK, you can probably count them all easily using just your fingers.
Secondly, Reading to Plymouth must be getting on for a couple of hundred miles(?). In comparison, Tyne Valley from Carlisle to Sunderland is about 75 miles. By this summer, I will have spent a significant amount of my free time in the last 20 months in researching it and building it for BVE 2 and 4 - and, even then, the BVE 4 version still won't include the train signal warning system. So, scale this up for Reading to Plymouth, and you've got a project that would take a pretty dedicated individual the best part of three years to complete, if my own production rate is anything to go by. (Yes, if you had a team of people working on it, with, say, someone laying the track, and lots of others building scenery objects, you could possibly do it faster - a year perhaps - but remember, it's all in your spare time!).
A scout around on the internet will quickly reveal that the UK BVE community is probably already one of the most productive in the world.
If we want to see more and better non-fictional routes being built, we've got to encourage more people to start developing. I have offered numerous times, on this forum and elsewhere, to do my best to assist anyone who wants to start (based on my experience of RouteBuilder - yes, handcoding is also possible, let's not restart that debate again!).
So, if anyone has any practical ideas for encouraging more route developers, let's hear them here, then let's do something about it....
Regards to all
eezypeazy