I would really like the feature where it says how many achievements you are from the next percentage. I know this used to be a feature in Stats, and if it's been moved somewhere else let me know, but it was really useful for me as I tried to improve my Completion Rate, and I would like to see it back.
Status changed to 'Completed' - We actually do this already.
If you're on desktop (i.e. not a mobile device) then you will find this on your gamertag profile at the top. Simply hover over the Completion Rate at the top of the page to see a breakdown of this percentage and what you need to unlock in order to increase your score.
If you're on a mobile device, then you can click/tap the completion rate that is shown at the top of your profile. This is visible from any page on your profile so it's a bit more accessible than the desktop version.