Obviously with the release of products like the R1 and RX, there is movement forward on the rekordbox front and these products are certainly newer than the CDJ family. Even the XDJ-1000 which fits into the "single player" category has more features akin to what you're asking for - the touchscreen allows for these additional functions.
As for integrating the SP1, it's a fantastic unit and I too would love to see the ability to control more functions through it, but as it is a MIDI unit and the signal would have to be received by the computer (not a CDJ) to then interpret that information and send it to the appropriate player, it might not be possible, but I assure you that the engineers are always tinkering around and it wouldn't surprise me if one of them already jury-rigged one for this exact purpose. If that's the case, hopefully we'll see something in the future!