Please accept my apologies for replying in English :-)
Probably the easiest way to make a live cartwall would be to use the sampler support in Mixxx, and make a custom skin with large touch buttons. Or use the MIDI controller support to make a physical controller with switches.
If you wanted to integrate a cartwall into Airtime, I would suggest using a genre tag such as 'cart' and a custom search to display only files matching that tag. Then modifying the interface slightly so that there was a button or keyboard shortcut which instantly added the item to be the next item in the Now Playing queue, regardless of having a show selected or not.