I wonder how much difference you would see at AAA between a great and a poor farm system. I figure it goes something like this:
A good development system delivers 2 major leaguers per season. Lets take a simple 2:1 loss rate at each level in the minors - that's four serious prospects need to get to AAA each year, 8 need to get to AA each year and 16 to A ball. Since between a 20 round draft and the internation signings a team does take in maybe just under 32 new players each year - so 2:1 math at each level works out pretty close to the overall system average.
So, long story short, most of the guys at AAA are still going to be organizational fill and hangers on with no chance of making the majors. That's going to be true whether it's a lousy system sending one guy to the majors each year, or a great system sending 3. The impact at AAA is still isn't that big a part of the roster. I suppose in a better system the failures might be better - i.e. more 4 A players?