What's the obsession with Union Square? The Gap Fillers? Union Square is not the cause of bottlenecking on Lexington Ave.
Go back and compare the amount of time a train is stopped at GC or BG vs. Union Square and post those results.
Also compare the s/b to the n/b in terms of delays and dwell time. Congestion on Lexington is not something that only happens in the s/b direction at 14th st.
I'll look up the number of TPH that currently run on Lexington. I did this last pick, and posted those numbers. I'd say 25 TPH is the max Lexington can handle. Even if you can develop a signal system that's better than the current one, there are just too many daily occurances on Lexington that prevent the TA from having more trains on the road.