If you want to prevent the 'wandering' of draw and blow notes you could add a blow note repetition. You could for example double every 1. That was later called 'solo tuning' (and is regularly used in chromatic harmonicas): Every octave plays the same, but it needs one additional hole (+ one reed) to fill in the blow note repetition:
blow: 1-3-5-1'--1'-3'-5'-1''
draw: 2-4-6-7--2'-4'-6'-7'
I've fairly recently converted a pokerwork to play like this. Although the customer is always right I couldn't see any benefit but I've played the 'normal' layout 40 odd years.
Perhaps the customer is a life-long chromatic harmonica player and just thinks of fingerings in this way?
I can see this more with a harmonica as it gives you quicker options sometimes when moving through a melody (either written or improvised), but not sure the same would be true with a melodeon, but as I'm a melodeon newbie, I of course don't know.
It would be interesting to hear/see someone play a box with that setup so as to get a feel for how they negotiate tunes.