I like the idea of keeping the prospect draft at 4 rounds. It helps teams to rebuild faster since there are going to be prospects that the established teams don't have the roster space to keep (and therefore they are not going to be exercising all their prospect picks).
It also brings the focus more onto the higher minors, greatly simplifying the necessary research. Anderson Espinoza and Brendan Rodgers are no doubt excellent prospects, but my guess is that neither of them is going to see the majors before 2019. That's a long wait, but it will mean that there are going to be a couple more fringe useful cards available in future FA drafts, which also helps teams rebuild.
And, I will steadfastly oppose any expansion of the keeper lists to make it less painful to keep uncarded guys.