How about instead of a mount, we have a pair of "Boots of Speed" or "Boots of Quickness" or even "Boots of Striding and Springing"?

Boots of Speed - 60% speed increase out of combat

Boots of Quickness - 10% speed increase in combat (passive); 30% speed increase in combat, 2 min CD, using the in-combat boost puts the passive on CD as well

Boots of Striding and Springing - 50% speed increase out of combat, double jump distance (passive); triple jump distance (puts passive buffs on 30 sec CD)