You're proposing a multibillion pound railway and you're worried that
lengthening suburban platforms would be too expensive???

I agree with James. The plan is hopelessly unrealistic and it's probably a hoax.

Having said that, hopelessly unrealistic plans can be quite fun. I
have my own unrealistic (but hopefully not hopeless) crossrail line
plan:

http://homepage.ntlworld.com/james.dowden/xrail.htm