I saw the discussion about fixed vs relative few times in the lilypond ml.
I think it's a lot about personal taste and habit and personally I decided to stick to fixed mainly because I find fixing mistakes in relative mode is much more annoying than writing in fixed way....
But what if the editor would help a bit? What if you enter music in relative mode (don't worrying to specify the octave) but your editor would propose the "correct" (nearest) octave to add?
For example suppose your cursor is immediatly after
b'
and then you type
c
What if the editor proposes to autocomplete with '' ?
This is just an idea.
Best regards, g.