I use the SDJ-1 for playback of backing tracks as i am a Professional solo singer entertainer, working on the Costa Del Sol in southern Spain. My many years as a DJ back in the 70s / 80s taught me the importance of keeping your audience on the dance floor, with no big gaps between songs.

I find the SDJ-1 to be perfect for what i want... EXCEPT! Track search.
As a singer you are the focal point of the audience and it is not acceptable to be always fiddling with your gear and searching for a track takes too much fiddling!

I used to use a Denon Double Mini Disc player, very similar to the SDJ-1 and that was PERFECT!
In so much as, (In single play mode) If you were playing track 3, once you had pressed the play button track 3 was locked ON, you could turn the track dial and select the next track number you wanted to play and when track 3 had finished it automatically went to the track selected and paused, if in continue mode it would play the next track selected, leaving me to concentrate on the audience and not my gear!!

Your product has another market out there! Food for thought???