What do you mean by onboard hydraulics??
Is this tractor equipped with a front end loader??
If so, it probabally has a pump on the front that powers it. Tap into that for the BH and it should be pleanty fast.
If it doesnt have a FEL, you are going to need a BUNCH of weight up there to offset the weight of the BH.
But to answer your question, NO you shouldnt need a PTO pump. BUT if you dont have a FEL or pump out front, it may be too slow for your liking and you may choose to add a PTO pump. But it certainly isnt a requirement.