Or you could keep the grind, but make the maximum power difference similiar to 1000 at your weakest and, I don't know, 3000 gold in Warband MP at your strongest.
1. There was a play test were you could ignore stuns when you took less than 35 damage on a voulgier. It was broken
2. If an infantry player manages to hit a horse with a two handed hammer, it is through the fault of the rider or the effort of the infantry player's team.
3. Bump stabs are far from being an abusive mechanic. I quite like it from a game play perspective. There are other parts of cavalry game play I would nerf before I touched this.
4. You need to move sideways and/or jump while approching an archer if you are afraid of getting shot in the feet. Some of the best players can sidestrife point blank shots semi-reliably without a shield. If you have any infantry shields and their movement speed I would expect a good player to avoid footshots when soloing an archer 95 % + of the time. Dismounted cav are toast though.
5. Crush through weapons are slow and leave you without a shield. Even the lesser shields are gonna give you way more protection against arrows (and melee weapons if you are not skilled enough to block without a shield)
6. Shields can passively arrows when not blocked with actively. If you have a shield on your back it reduces all damage on your back by about 33 % IIRC. Should be a slight sound cue when it happens.