I've been experimenting with a way to create a measure-counter (issue 2445), and I've come up with the attached Scheme engraver. The music within a count doesn't need to be repeated to use it.
This creates a new grob, MeasureCounter, which you can override in various familiar ways. If you find that the number nestles in too close to the music, for example, you can do \override Staff.MeasureCounter #'outside-staff-horizontal-padding = #1.
You can also override 'counter to start with a different number if you like.
It's possible to have independent simultaneous counters on different staves.
The examples are written to work with the latest versions. (I'm using the current release candidate.) This engraver should work with 2.14.2, but you will probably need to change the position of \measureCounterStart and \measureCounterEnd.
I'd love for people to try this out, to see if it works in situations where you might want such a thing. (If you have a suggestion, see a problem, manage to break it, please do let me know!)