I think it'd make sense for shield stats to have a small influence on the nudge effects, eg:
Higher armor = more damage
Higher max hitpoints = greater shove distance
Higher weight = greater shove distance, greater damage, longer nudge animation
Higher speed = shorter nudge animation
Greater size = greater shove area (range and "arc"), longer nudge animation, less damage
Would probably be a pain in the ass to balance it all out though, it's easier to just give smaller shields better speed/lower difficulty.
It also makes sense for some other nudges like pole shove and 2h pommel strike to vary by weapon, but that's another topic.