"Empty" stave with exactly placed barlines

[Urs Liska]

I know it is not how LilyPond actually thinks and is supposed to work,
and it has been discussed from various angles. But I'm afraid I have to
ask (again) from my actual challenge's perspective.

The task is to produce empty staves to replace staves in a scanned
score, i.e. to create an empty staff with some white space around it
that can be superimposed on the scan.

Question: is it possible to create a staff without content but with
barlines placed exactly at requested positions (e.g. expressed in
millimeters)?

As a bonus, would it be possible to create an empty (i.e. non-visible)
voice where note-columns are positioned exactly. This doesn't have to
have any notion of meter (e.g. an arbitrary meter or a cadenza); the
task would be to position lyrics or bass figures exactly below objects
on a scan, e.g. adding musical analysis on top of a scanned score.

It would not matter if the required code is complicated because that
would be generated by some tool that would have marked up the scanned
image in a graphical environment.

Thanks for any ideas
Urs

PS: Additional reference: 
https://github.com/frescobaldi/frescobaldi/issues/1271
https://github.com/frescobaldi/frescobaldi/issues/1271