I gotta agree with PFF. Known bass are, to me, a better bet. You don't take the chance of introducing "unknowns", including disease, into your pond.
However, there is another thing to think about. Research indicates that 1/2 of the bass in a pond will never bite a lure. Their progeny is also hook shy. I like the idea of being able to stock bass that will bite and thus having their progeny showing the tendency to be "catchable". I'm not sure that bass from a bass heavy pond really fit that criteria. Those suckers would hit spark plugs or tennis shoes.
If I have to restock, I'm going to try that. First establish a forage base and then catch bass from a lake and stock them.
Just my $.02.
