IMO the nice way to do this would be to add a "conservative"-option
to convert-ly. When conservative is on, convert-ly tries to stay as
close as possible to the old syntax (i.e. keeping "times"), when
conservative is off, it tries to use as many of the new constructs as
it can (ie. translating times->tuplet). Of course we "could" (sigh)
expand the use of the conservative option to lots of other
constructs.
Like \relative { => \relative c' {
This would take a lot of time, but adding the skeleton,
i.e. reading the option from the command line and making it
accessible from the convert-ly-rules could afaics be quickly done by
a python-hacker.
Well, this is always the problem with open-source: it takes to
time implement new features, and then it takes time to maintain
them. (that said, this could probably be done in such a way that
maintenance is not an issue)