We have an issue when a page is deleted/ unpublished someone forgets to add a redirect.
Now what i am looking for is when someone is about to unpublished a page or delete it, we pop something up that will offer a user a list of pages and they can select which one it should go to.
Any ideas where I should start with this and what hooks I could use.
There is a module that does much of what you describe: Save Redirect on Delete. It will push the user to a predefined page and you could put popular items on that destination page.
If you want the recommended content to be customized for the page they tried to reach you'll almost certainly want to build something custom. This module would probably give you a starting point, but in addition to what it provides you'd also need to preserve some kind of taxonomy reference (or similar) information to be able to provide something sensible.
Another option might be to use Rabbit Hole and instead of deleting, just change it to a redirect:
https://www.drupal.org/project/rabbit_hole
While this may not be an exact answer/solution to the original post, it may serve as an inbetween to make it all work.
