These problems are all tractable using traditional computer vision methods. There's a sizable body of published academic research from the past couple of decades that addresses tackling these and other computer vision problems in the specific applied context of video analysis of soccer games. Considering the amount of knowledge out there I'm kind of surprised that any clubs at the premier league level are still in a position where they aren't able to extract useful information from their library of game footage. With so much money at stake I figured that even if clubs weren't developing their own analytics tools in-house there would be no shortage of third party tools out there by now.

>I have people inside a Premier League club just waiting for me to be able to throw OpenCV at an archive of video

How extensive is the footage in their archives? i.e. is it just what winds up in the broadcasts, do they keep every second of footage of every game taken by every camera in the stadium, or is it something in-between?