A continent-wide network of roads and train lines is an excellent idea. In fact, we already have one for roads.
https://en.wikipedia.org/wiki/Intern...E-road_network

What isn't a great idea is "mandatory goals" and all that bollocks. You've got the continental authority saying to the pesky little nation state "well you can only join if you make sure you trains are fast enough".

It's just a map. Not adding the UK doesn't mean that there's no roads or train tracks in the UK. What it means is the EU won't add us to their map network, any nobody will care nor will anyone be the slightest bit inconvenienced.