If you're convinced higher OPI leads to WR's making better and more aggressive plays on the ball (I'm still unsure myself tbh from different things I've seen), why not dramatically lower DPI and really bump up OPI to maximize this sliders effect? So instead of a +25 OPI differential, have a +50 or +75 or even +100. Whatever the max is without breaking the slider.
In this game, DB's make too many unrealistic plays on the ball that you don't see on Sundays. Meanwhile, and more to the point, WR's are far too passive and don't fight enough for contested 50/50 balls. If you could have the WR's playing to their max aggression and the DB's only playing at balls their eyes can see and in a realistic radius to them, that would enhance the passing game greatly. I understand increasing the slider differential could loosen coverage too much (I'm guessing), but if that's the case, you could simply bump up pass coverage to make the coverage and windows much tighter. Ideally, you'd have a passing game with tight windows and coverage, but WR's fighting and winning more of the contested 50/50 balls. Elite QB's would shine more due to fitting it in tight windows and making good reads, and below average QB's would struggle more due to inaccuracy and poor awareness vs tight coverage.
All sounds good (to me anyway), but not sure if it would work that way. If OPI/DPI works exactly as you think but, and from what I can tell pass coverage slider works as it should, it could be worth a look-see. Chances are you've already tested this but. Thoughts?