Real talk question but why is there not a bus route that travels from the start of Neptune Avenue in Coney Island, then along Emmons Avenue toward Knapp Street, then up Knapp Street to Kings Plaza? The B4 stops short and with this sort of route you would give Coney Island/Brighton Beach/Sheepshead Bay riders a direct route to this mall, and provide some sort of bus service on Knapp (which is such a pain to get to).
The B4 can instead continue straight down Avenue Z instead of doing whatever nonsense it currently does, and this route could replace service along Neptune.
Something like this: