I was thinking of that but others said not needed--had originally. If I disconnect at the unions, only a bit of water will need to be "caught" in a bucket as the water won't flow in past a certain point--dursa stands. Once water falls below that, there won't be any more. When we get it started, I'll see if we want the extra bit of safety there. With unions below, wouldn't need true union balls, unless you can disconnect a true union ball and still have the "ball" part in tact?
With regard to the Cepex ball valves I believe you can remove the union with the ball valve intact.