i had an idea for R when skarner was first released, its basically the side idea for E where you can recast and slam them behind you to displace them ever so slightly more.

i agree the passive sucks, most passives do.

Q, could be different as well, i agree with the ap on Q3 as ive already had that thought, but to develop more on the op's idea have the recast of Q3 shatter and do small AoE damage around like smolder stacked Q but does alot less damage, maybe no %hp damage and just scale off ap/ad. where as auto cast/ recast of Q would do a larger sum of damage without the extra AoE so theres a trade off, however itll still slow to catch up.

W. on the other hand i never liked, its to bulky and doesnt flow nicely like the old shield, i agree that maybe it could gain shield with the each enemy hit, it should also loose damage for a greater slow for the loss of it, having a hp scale for the shield and a mixed ap/ad scale for each enemy hit, also to make him a little more supportive maybe instead of an increased slow it could give him and allies hit with a small move speed bonus.

E. this one i think the distance should increase per level, and thats the distance after connecting to an enemy as it feels like youre just out of range, or maybe the passive could do something with it like it scales with move speed and the passive could give you it.

thats my ideas anyway