The B23 is a loser of a line that has been a loser of a line for pretty much its entire existence. Trying to extend it (and instituting both extensions would more than double the end-to-end mileage) is throwing good money after bad. Also remember that the longer a route gets, the less reliable it is likely to be (ask any long-time B11 rider about THAT).
The frequency of service is determined by ridership levels. The B23 barely merits what it's got, let alone more service. As to what buses would be assigned to the route, there are currently no 9200/9300-series soft-seaters in Gleason, and adding them would entail instituting a new parts inventory (for the seats at the very least) at that depot. Moreover, for local routes that use 40-foot equipment, there are no dedicated fleets -- under most circumstances the Yard Dispatcher gives the next bus that's ready to the next Operator who comes up to the booth.
As to schedules (customer timetables, actually), they ARE available. Local libraries carry them, the buses are supposed to have them (yes, I know it's rare), and anyone who wants one and can't find one can write to NYCT and request one. Additionally, each stop is supposed to have a Guide-A-Ride that lists every departure.