As a regular CPW rider, I personally think that CPW is undeserved. I also believe that 6TPH is unacceptable for this route. (Not to mention Fulton)
1. Well the

and the

make more than 6TPH. BUT, a

almost ALWAYS comes right after a

making it useless unless you just missed the

. (Which has benefited me a few times, but nevertheless)
I believe either the

or

should be rescheduled, so that they don't come relatively close to each other.
1A. The

doesn't run on weekends, so we're stuck with only the

, which comes less than every ten minutes. This is straight out unacceptable, which is why another possible solution, would to have the

run on weekends. (This is assuming the scheduling problem is fixed)
1B. Extend the

. Now in terms of the weekend

extension, I do think QBL would be best. IF that wasn't do-able for some reason, then the

should be extended to 145th to replace weekend

service in Manhattan.
2. Make the Cranberry St Tubes four tracked. Now while I understand how difficult this would be, since they are building the Fulton St Transit Center now, this would definitely be the best time to build it. This way, the

could have an increased TPH, while the

is unaffected. And unlike option 1, this would also benefit Fulton riders.
Ways this could work;
2A. Have 8th Ave be 6th tracked for a short section of track after Canal St, then after the

diverges, it would be four tracked. As I said, if this is going to be done, it needs to be done NOW, because we can't tear up lower Manhattan twice. It would then in Brooklyn use the

tracks at Jay St, and the abandoned tracks at Hoyt.
2B. Extend the

tracks to connect with the

again at Fulton. It would then run four tracked.(See 2A) Now I am aware that this would make Chambers St an express only stop, and that the

couldn't terminate there. But this would provide extra service to WTC. As for the

it could run as the Culver Exp. Just saying. Yet again, needs to be done NOW.
3. Send the

Via Rutgers. This seems like the easiest solution. Now this would make Chambers/Fulton/High St all

only stops, but all the switches exist for this idea, and the

could have an extra TPH, while yet again not effecting any lines around it, and it would give 2nd Ave, two trains again.
I would personally go with idea 3, (And 1 if possible), what do you guys think?
P.S. In idea 3, it would benefit Fulton aswell.