Hadn’t realized you were talking about Apps that don’t support AB. Not a surprise that you’re getting blank audio in Cubasis as AB is the only way of bringing in live audio.
I suppose you could mix down to another device or use ACP to bring the tracks in to Cubasis once you have finished so it doesnt break up your creative flow and mix down from there.
Virtual midi is still really useful. You can work on your performance editing as required then record into Cubasis via AB once you are happy with it. You can also get several parts working together before recording each in its parent App and then using ACP to being them together. Maybe most importantly you can record the midi whilst feeling creative then do the AB or ACP task when you’re finished recording.