This is a neat idea. A bloke over on modularpilot.co.uk (I'm not affiliated, it's just a good blog for modular pilots) submitted a freedom of information (FOI) request to the CAA for ATPL pass rates. The graph doesn't show retake rates but I'm sure they can be FOI'd too. Check them out here ->
https://www.modularpilot.co.uk/atpl-...2013-2018/2138