@Javier
Just no. You already got the M34 SBS, which is enough, plus, you can use nearby stops on the 8th Av line, 7th Av line, 6th Av line, Lex, Broadway, and soon, SAS. Do you do not notice why exactly is the 42nd St Shuttle a shuttle in the first place and is accepted? Grand Central is a major train station, and Times Square is a major train stop and some other major things. A shuttle allows trains to connect with each other faster so passengers won't suffer. Your 34th St Shuttle is nearly useless.
Do you notice how far apart your stop are? You will basically have each platform literally 12 ft away! A single platform is about between two avenue's length. Half of that? Still, half an avenue's lengh. This proposal is not really someone would utilize.
Relax, just calm down. Please.