First off, thanks for this very helpful plugin.

I use this plugin to monitor for systemic stability issues and keep the relevant build artifacts when issues are found. Then when I have time, I review these artifacts and identify the most common issues.

One feature which would really help this use-case, which I think may be a minor change, would be to add
'keep all unstable and failing builds'.

There may also be use-cases for:
'keep all unstable builds'.
'keep all failing builds'.

But for our particular case, we'd ideally want to be able to use 'keep all unstable and failing builds'.