IMHO the easiest path to achieve what you want/need could be improve audio recorder GTL functionality (and click/drummer track).
Audio recorder should have multiple lines/tracks and some kind of markers (cue song parts)
Click/drummer track should have song mode (think in a groovebox) with chainable patterns and midi control of these patterns. Editor will be handy but something like sdrum pedal maybe will be more useful.
https://youtu.be/U8E1poBX_uA
Dedicated mixer/bus/fx system outside the slots. ATM is useful but the whole metaphor seems working against multitracking management on timeline.
About slot choke and so…
I will suggest keep the channel count low (8 audio looping tracks) and maybe main group apart. Midi track for click/drummer should be a thing it’s own. Then grow from there in complexity. Midi looping has it’s own drawbacks (all in my Humble opinion of course)
Garageband drummer based on sdrum could be like trio+ band pedal iPad version.
https://youtu.be/dmFuL1yAglM
https://youtu.be/JC2eu03_oxY
OTOH @[deleted] Did you tried lumbeat apps? What you are performing in the video is faster and more powerful from the combo of iBassist and some drummer and you can link those with actual GTL (or anything). It’s the most powerful arranger (think in ketrons) I have found.
It’s like Trio+ but with midi/audio export (digitech pedals are a bit limited).
https://youtu.be/jCa9XAjnUtY
Another option could be Beatbuddy pedal.
https://youtu.be/GnaQnn24I-M