It would make more sense to just make them like weapons: Difficulty based on strength, shield skill has more tangible effects on speed/coverage/shield bash than all of these hidden values with a slight general buff to the skill. The prices would need to go up considerably more than what they currently are, maybe up to 9-10k, just so mid-value shields can get used a bit. Final damage mitigation is crappy for a skill all by itself (with unknown speed/coverage where we don't even know if even works the way we believe). I also thought that shield stats may need to be changed, but maybe not as much as previously thought in its current condition.
People are going to hate what I say next, but the offensive shield bashes with high shield skill should deal a decent amount of damage and have a better passive block effect against projectiles. Currently, it's foolish with little reward to try a bash in front of a held shot, and worse than most of the other nudges. I'd rather use the 1h nudge for offense and the polearm nudge for defense.
The disparity between not being able to pick up a shield vs. the nature of shield skill conflicts with eachother gameplay-wise. Shield makes sense for agility, but it doesn't make sense as a difficulty requirement based on the current shield animations. This game doesn't have any techniques or the like that makes me believe that you have to be well versed in the way of the shield to hold up a Huscarl's, unlike being properly trained to ride an arabian warhorse.
Even so, doubt much will really happen in the end.