A couple options. Can be mixed and matched
scattergun damage/knockback nerf
A damage nerf of the scattergun to be the same as the soldier/pyro/etc shotgun would be a 10%ish decrease and would also linearly lower the knockback to deny rocket jumps
full damage meatshots won't 2 shot a 200 hp soldier anymore. On paper a big nerf to scout, though in practice more subtle since 200 hp soldiers aren't that common. Though it would encourage tanking demo/pocket soldier more since they'd be harder to wm1 into as scout.
Further decreasing knockback to be around 70% of what it currently is would be fine (imo)
Scouts can still deny, but a fast moving soldier will be way harder to stop in its tracks
medic speed buff revert
Already discussed plenty in the past so not going to write a paragraph about it
soldier/demo buffs
Further decreasing base rocket/sticky jumping self-damage. Making gunboats apply damage reduction even if you hit an enemy target. self-damage should never take more than 30 hp imo
idk about this one
Making soldiers walk at demoman speed? Would make it easier for soldiers to lead in an uber trade through chokepoints. big Rando buff
edit: I agree with YeeHaw's comment on page 2 so nvm the scatter damage nerf (though knockback nerf definitely still a viable option)