Łukasz, you raise an interesting point re the arpeggios. The feature of the above layout that most concerns me is that the fifths are directly above the roots, which might impeded a I-V jump. One idea that comes to mind is to shift the "F" row over one notch to the right, making a C to G a diagonal-up-right shift vice a straight vertical, allowing an index finger to hit C and a middle finger to hit G. That would have the downside of swapping the awkwardness to the fourth, but that's slightly less-bad than the fifth being awkward.
Is it the opinion of those gathered that there's no comfortable way to convert a Maccann simply by moving reeds around, that any viable Hayden conversion must entail making new ends and changing up some of the keywork and reedpan?
Even if it sacrifices some comfort, I see much more appeal/convenience/affordability/reversability in simply moving reeds about with no changes to keyword or fretwork. Is that not what the Cheeseman system did, preserving all basic structures while largely moving solely the reeds about?