It would be nice to be able to add your own loops to the looper in order to take advantage of the time stretching algorithm. Even if there was a time length or bar length and they needed to be processed before hand.
The djay Pro Looper only works with the built-in loops provided by Algoriddim.
But you can playback custom loops by using Ableton Link and an external app. The Ableton Link will keep djay Pro and the external app in time / in sync.
Many pro DJs use Ableton Live for loops, but you just need an app that supports Ableton Link.