I'm sure someone has brought this up before, but I've been thinking a
bit about the way users tweak output in Lilypond. As it is, tweaks
are generally interspersed with actual music information. This seems
to make things difficult when someone tries to maintain a part that
has to be transposed a couple different ways, or printed on different
paper sizes, or whatever. The web deals with this problem through
CSS, and I would suggest that Lilypond might do something similar: let
users name timesteps, timestep edges, measures, and categories of
such, and format them according to a separate program. Obviously this
would be loads of work, and I don't even know if it would be feasible,
but that's what I'm thinking.