The football manager database is widely used within the game. The network of scouting that SI have is massive and way beyond what any of the actual clubs have and goes into pretty much every country you can think of. They actually make a special version of the database for clubs to use, it's merely a tool like every other resource though.
Yes, we do need our own resource database but the best way of doing that is to look and take information (no matter how big or how small) from anywhere, if you take Brighton, they have a team of people who watch and record the details of every single professional football match in every league each week in every country around the world, then they narrow things down from there.
The going back in history thing is a bad idea imo, the game has moved on and what was required in certain positions previously is very different now, look at Goalkeepers. Gone are the days where they just stood there waiting for some action then did a few star jumps or a superman dive, these days a keeper is expected to be able to pass and dribble the ball halfway up the pitch!
Key metrics for positions, well tbh if we are not doing that in our recruitment already then we should be imo.
