Since I started this thread I discovered that I can barely make a 2 to 5 fret stretch on the 4th string, so having an even longer scale for that string would be even worse for me.
Tomorrow I'm going to tune our Mikro down & finally prove to myself that I can play that song with the 2-5 stretch.
I also think that balanced-tension string diameter takes away the majority of the issue with a one-dimensional scale-length.
It boggles my mind a little that there are string-sets out there with diameters like 0.05" - 0.10", completely imbalanced tension!
A 0.105" as the 4th string when the 1st string is 0.045" is also imbalanced, just not as badly, but it gets worse when you down-tune to Drop-D or Drop-C.