I liked HW's slow grenade as a concept because it doesn't interrupt your trajectory, just imposes a speed limit on the scout/medic car.
Whereas the overpressure causes a 3-car pileup on the 405 type deal.
Yet with only 1 slow nade and it lasting 5 seconds it never felt like I could be a traffic cop long enough.
What about removing overpressure and moving the slow nade effect to right click? i.e. every 20 seconds HW can right click and causes people in a small radius around him to slow down for 1/2 seconds? (Particle effects would have to accompany to show that it's active.)
This would still require him to maneuver to where the scouts are coming (my skill cap!) but not be so annoying with the farting and trajectory interruption stuff.