Unfortunately I can't use ACC going Downhill
 

Because ACC maintains the speed I set, it will not let the car coast above the speed I set (as a normal cruise control does). Therefore on steeper down-hills, the ACC "rides the brakes", so I don't want to use ACC in this situation. I would like Audi to have an option for me to defeat this capability, and if the car drifts up in speed, let it happen. This would be easy to do by setting an algorithm that says, "If a vehicle ahead is detected then brakes are used to maintain speed, if no vehicle ahead, the don't limit the top speed."

You can try downshifting which will use engine braking (little fuel is used) and save your brakes. FWIW.

Firstly, I wish Audi allowed the option of choosing CC or ACC, that would satisfy your dilemma.

Secondly, I not sure that I would want what you are asking for: cops around here tend to sit at the bottom of gradients knowing that cars will drift upwards in speed going downhill and it's an easy ticket for their revenue generation. The Audi ACC keeps the speed I set whether its too fast or too slow.

Don't see why it would solve the issue. CC will still maintain a set speed going down a hill using the brakes to overcome any acceleration. Main reason why it is easy to better the fuel consumption driving the car yourself that letting CC or ACC to do it for you

I'm not familiar with the C7 non-ACC CC but what you say sounds likely. I think the OP wants ACC to decelerate as he approaches traffic. At least that's the only thing I can take away from his wanting cruise-control which doesn't control his speed....

I think what he wants is for the car to detect an impending collision and adjust speed accordingly but unless a collision needs avoiding it should be allowed to accelerate beyond the set speed to an unlimited speed thanks to Mr Newton's forces. As DB22 says traffic cops tend to put speed traps at the bottom of the hill for just that reason.

I would love to be there when he explains it wasn't his fault he was going too fast it was Mr Newton's! Bit like the guy who posted on the Apple Support forum this morning asking who he should contact because he crashed his car trying to reconnect his phone after the bluetooth connection failed

I have ACC and I don't have a problem. I want it to keep my selected speed. It was dicktahoe who implied that CC allows acceleration downhill and that ACC does not.

dicktahoe will have to advise but I think he just wants his cruise control to allow for Newton to increase his MPG.

I see his point and have experienced this phenomenon myself so I just turn off ACC and let it roll. I also subscribe to the theory that if you have to use brakes then you have just wasted all of the gas that you used to get to the speed that you now need to brake from.

I'm not sure I understand why when using the ACC one would want to go faster than the set speed when going down a hill than going up a hill or on the flat. The whole point of ACC (or standard cruise control) is to maintain a set speed. I guess the simple solution would be to temporarily flick the ACC lever off if you want to go flying down a hill unimpeded by the set speed.

When on a steep hill I just shift manually into a lower gear while leaving ACC engaged, works perfectly, brakes don't come on (esay to tell if you have a big chrome bumper Kenlworth on your butt)