Juggernaught demigriffon knights and ogre sabretudk riders all have the wounds of the mount, i think all monstrous cavalry do. It is a like for like replacement. I did a chaos dwarf on a juggernaut to count as the larger centaur hero in wap 8th or 9th. It has 4 wounds.
I dont really like the large centaurs, they seem more like dragon ogres to me but less cool. So yeah alternatives for me. Zanko has a a unit of juggernaut riders in his blog. The bears would be a somilar proxy
And theme -wise we can all do whatever we want!
There are so many variants in peoples blogs here. We are in theory an obsolete army…although it is going from strength to strength these days