I was at one point very interested in the same idea. I wanted relative line numbers and absolute line numbers integrated together. So, I created a patch, called it `dnu` for "dual line numbering", and sent the suggestion to Bram Moolenaar.
However, in 7.3.787 (Jan 2013) a patch was introduced which showed the current line number in :rnu instead of 0. That's definitely in the direction that this patch was going in.
So, I didn't get a patch in, but on the plus side, I did learn a bunch about vim's source code.
Here's what it looked like: http://i.imgur.com/NTwwB.jpg
Here was the patch. I wrote it back in 2011: https://code.google.com/r/justinvh-vim/source/detail?r=c2479...
Ultimately Bram Moolenaar sent me a reply:
"""
Justin,
I think the audience for this would be too small.
- Bram
"""
However, in 7.3.787 (Jan 2013) a patch was introduced which showed the current line number in :rnu instead of 0. That's definitely in the direction that this patch was going in.
So, I didn't get a patch in, but on the plus side, I did learn a bunch about vim's source code.