Three plus years ago I posted about adding an alert that would let admins know when endpoints weren't scanning. At that time you said some new alerts would be introduced toward the end of 2018, but I haven't seen any new ones. I'm not always in the console and there isn't a column or report to easily view this info. An alert that endpoints a, b, and c haven't scanned in x days would be useful. Here's a link to my original feedback post.
This feedback post also has some very useful points on improving reports that could also be used to improve alerts too. I particularly like the idea of branding things with our logo and making the emails and reports more visually appealing.