Mark some revisions as important for skip auto delete

When active updating content of site - many nodes have too much revisions. But some revisions are created with fixing small typo mistakes, but other - grand update of content.
And totally cleanup all revisions will be not so good way.

So will be good to have feature for mark some revisions as important, for skipping it from auto deleting.

Good example of this feature you can look in Joomla 3.x version, here is screenshots: http://www.inmotionhosting.com/support/edu/joomla-3/writing-articles/ver...

How to prevent a previous version from being deleted

If you don’t want a particular version of an article deleted when the Maximum Versions limit has been reached, you can lock the version to prevent it from being removed. To lock a version, on the Item Version History screen, simply click No under Keep Forever. This will change the value to Yes, and prevent the version from being removed.

So you can mark version as "Featured" and it got flag "Keep forever" so will be never cleaned up.

We can take some ideas from #3072289: Data Retention Functionality →