by speed, do you mean both movement and attack speed?
hmm, probably the only way to do this is to make an ability based off either endurance or vampiric aura, then make another ability based off an item ability that gives the same effect, i.e
i make an ability based off vampiric aura, but description shows stats for both lifesteal and attack/movement speed
i make another ability based off item attack speed (or something like that) then add the ability to the unit.