Even if you didn't run the express, you could still fit the into Forest Hills. But why add merging delays for no good reason? And like it was said before, the express tracks are full. Unless you want to reduce service, which would be a nightmare.
The bypass will be a waste. There is better demand for it to connect to east of 71 Av than go to the Rockaways. The is already direct to Midtown, and the would be the direct express from the Rockaways. Plus, most of the ridership will be north of Aqueduct Racetrack, already close to QB.
Why have it terminate at either? The already would almost mimic the route from Rockaway Park to Bway-Lafayette. And do you really think WTC can spare more trains since the is at 15 TPH?
I do agree on having Woodhaven converted, but the LIE line should be the via a new Myrtle Av bypass out to Little Neck Pkwy. The would take its place on the Brighton Line and the will take over West End. Branching it off of QB will leave 67 Av as a -only stop.