The common division of the octave, 12edo, doesn't have a problem to define sharps and flats:
[C] [C♯/D♭] [D] [D♯/E♭] [E] [F] [F♯/G♭] [G] [G♯/A♭] [A] [A♯/B♭] [B]
Bold texts indicate black keys.
19edo doesn't, either:
[C] [C♯] [D♭] [D] [D♯] [E♭] [E] [E♯/F♭] [F] [F♯] [G♭] [G] [G♯] [A♭] [A] [A♯] [B♭] [B] [B♯/C♭]
It looks like white keys are to approximate dedicated just ratios:
C = 1/1 D = 9/8 E = 5/4 F = 4/3 G = 3/2 A = 5/3 B = 15/8
And it looks like sharps and flats are to approximate the chromatic semitone, just ratio 25/24.
This logic applies to 12edo and 19edo, but let's apply it to 53edo. 53edo would have the following names for keys:
[C] [C+] [C++] [C♯] [C♯+] [D♭-] [D♭] [D--] [D-]
[D] [D+] [D++] [D♯] [D♯+/E♭-] [E♭] [E--] [E-]
[E] [E+] [E++/F♭] [E♯/F--] [F-]
[F] [F+] [F++] [F♯] [F♯+] [G♭-] [G♭] [G--] [G-]
[G] [G+] [G++] [G♯] [G♯+/A♭-] [A♭] [A--] [A-]
[A] [A+] [A++] [A♯] [A♯+] [B♭-] [B♭] [B--] [B-]
[B] [B+] [B++/C♭] [B♯/C--] [C-]
The keys represented with italic texts would have a hypothetical 3rd color (say, green).
Though these names fit C Major scale and C natural minor scale, they won't to scales based on other keys. Say, G Major scale. The usual definition of G Major scale is:
G A B C D E F♯
But shifting the C Major scale to G actually gives:
G A+ B C D E F♯+
Furthermore, since this definition of names of keys gives accidentals smaller than ♯ and ♭, the usual definition of scales cannot be applied to scales based on "green" keys.
So my questions in summary are:
How did sheet musics for instruments in 53edo overcome this problem?
If I choose the usual definition of scales, would that mean I have to choose the tonic according to musical key characteristics by Schubart?
If I shift the C Major/minor scale to another note, would it be too hard to play on a hypothetical 53edo keyboard due to the "green" keys?
Would it be inappropriate for a scale to have a "green" key as the tonic?