This is exactly how I do my fantasy football rankings. Project stats for the whole league (the hardest part, I usually download a few and merge rather than do my own), apply the league scoring settings to the players stats to get fantasy points, then determine how many standard deviations above or below average each player is.
It's great for fantasy football, because all that matters is numbers, not their context.
It's value to real football is limited much like any offensive stat is, it gives no weight to the context of the stats. You're also assuming that each of the 4 statistics you look at for each position are all equally as important and the only 4 things that matter. I've got no idea which stats matter the most, and how they rank compared to others, so this is as good of an attempt as any, but I'd be curious in knowing how you determined the recipe for each position.
For baseball, the goal is almost always the same, so you really only have to adjust for park factors. In basketball, the goal of each possession is almost always the same, so if you only have to account for tempo or make the stats per possession. For football, there are just so many variables. The goal of every play is not the same, some are designed to get you the 1 yard you need, others are low percentage chances of getting all of the yards, some WR go deep a lot so you wouldn't expect many catches but would expect high YPC and vice versa. Some offenses run 60/40 others pass 60/40. Some teams have great offensive lines that help their backs and QBs produce better, others vice versa. Some WR get to catch passes from Tom Brady or Aaron Rodgers, others have to have ducks hurtled at them by current-era Peyton Manning or Ryan Tannehill.
I have no idea how to resolve all of those concerns with football when trying to compare multiple positions across the league. I doubt it's possible. I like seeing people make attempts, though. It's definitely an interesting analysis, I just wouldn't use it to make any sort of conclusions.