Support items should build up leniency time
If I spend 3 minutes within 2000 units of my adc, I think I should have like, 30 seconds after they back where I can still proc my supp item. 1 second leniency for every 6 seconds of codependency wouldn't open up the zero cs strategy top lane, but would allow adcs to back without heavily delaying their support. This would make first back more generous since you'll have buildup time from pre-minions, but would still promote lane dependence.