I do. It's basically why the stopped running east of 71st Avenue only a few years after it started.
You would've been better off seeing the station for yourself before saying that, considering where the crew rooms (yes, rooms) are located. (The layout also makes running the existing 18 trains quite the adventure.)
Technically, they can have trains depart from either track, but it's easier for people to know which train is which based on the track.
Why run two Bronx routes in a manner where they hardly support each other, and why do it with Lexington Avenue?
For that matter, why inundate those stations with more trains than they need, and why not focus on providing more support for Bronx ridership?
In Brooklyn, service up the West Side is largely an afterthought for riders, yet the Bronx is rather starved. We don't have any half-decent places to short-turn trains so they can serve Manhattan-Bronx ridership more effectively, and merely running more of them only addresses the issue of merely serving the Manhattan-Bronx ridership.
Have you actually seen how a Lenox-180th/Unionport/239th move would look? It's not pretty, and without some sort of change to the track layout, it'll remain horrifying. We can also forget about a good chunk of existing service and probably those two stations in Harlem. (Before anyone tries to claim yet again that the MTA wouldn't dare to do anything of the sort, just look at what happened with the Queens draft, especially with the Main Street buses and the Q53.)
You'd be able to achieve that now by having better and timing at 149th Street and not having trains to/from Brooklyn use the middle track.