Team overalls don't tell us much, it has much more to do with individual positional overalls. Every specific position requires a different set of min-max values, that's the key. You can lower a FW's overall rating into the 20s even while assigning him 99 in finishing and shot power, and he's still good for scoring goals at least. But the only way to create a 20-rated CB is to lower his defensive values way down, at which point he becomes entirely useless. General ballpark numbers:
Effective FWs can be 20-99.
CBs can be 40-99. Any lower than 40 and they're pylons.
GKs can be 60-99. Any lower than 60 and they can't save a beachball.
That sort of thing.
Many positional players in my db are rated 30s and 40s and that works for me. But it all depends on what you want to accomplish with this project, and your original ideas about a viable ratings system are no doubt more realistic. Few people here will play FIFA with players rated 30s and 40s, that's the reality. They want to see their favorite players and teams rated 60s to 90s.
I have no illusion that everyone will adopt and apply this. I do, however, think that certain patch makers could and should at least consult it. At the very least, it's a quantitative way to address large discrepancies.
I think you're thinking that the equation is saying 'this player should be exactly this good and everyone should conform to that value.' I don't think that's the right way to do this. I think the right way to do this would be to consult this first, then apply your own tweaks according to your own specific knowledge.
So, if a patch maker puts out a patch that has EPL quality players coming from Estonia or something, you can start to adjust or suggest an adjustment.
It's not, John Blowhard IV should be a 45 and no one should think anything different. It's, John Blowhard IV is overrated according to the quantitative system. And that degree of overrating is approximately 30 points.
I think experienced people will always have their own opinions about other details. That's fine. I do urge you to try to quantify those differences, however. In that way, the quantitative system I developed gets you close, the quantitative adjustments proposed by others can then be applied for greater realism.
If you just have vague notions of rules or procedures that work for you, no one else can replicate that. It will, forever, live in your head. However, if you try to quantify those differences, others can try to apply your changes and see for themselves if your approach is one they would like to adopt.
None of that is criticism. It's an urge to try to quantify what you're saying so that the community can either decide to adopt or reject your approach or tweak.