connecting a usb device to aux on DJM-250Mk2

Hello, i have a question for my DJM-250Mk2. 

I have hooked up a pair of CDJ-400's with usb, a MacBook Pro with rekordbox 6.0.3, a DDJ-XP1 on my DJM-250Mk2.

So far no problems and using it (to my capabilities) to its full extend.

I had the configuration connected with either the USB and cinch audio cables. But removed the cinch audio RCA cables due to the fact that i am only connecting my CDJ's, XP1, DJM and MacBook with an USB 3.0 hub and all the connectors on de DJM are in USB mode.

So no need for line in audio/RCA/Cinch cables, which will delete clutter at the back as well.

For some time though a had a single RCA/Cinch cable hooked up on the AUX port and it was, off course, in line mode. So i could add Eg. an IPhone with Spotify or anything else just for requests etc.

i do not use the Microphone port, so it was the only analogue port used.

But my thoughts where on the Line/Phono/USB connectors this morning and therefore as well on the Line/USB of the AUX port. 

As i have read in the manual i can add a analogue device through the AUX>Line or i can add a digital device through the AUX/USB. 

My question is, will it be possible to add a third CDJ or sampler etc to this AUX/USB connection and show up in Rekordbox. Eg. i add a CDJ/XDJ/SPJ to it, which will show in recordbox a unit 3 and although i can not alter the tone settings, i can beat sync it etc with Rekordbox and play Eg a beat sample or any other to use as a base beat. And then can use Deck 1 and 2 for additional tones, samples, music etc?

I hope i have been clear enough on my setup and wishes.