The changes for managing all of this sound really good!
My feed hasn't gotten too unweildy yet, but I can see how it could easily become a problem.
The showcase sounds awesome! It would just yet another way to make your Newgrounds profile your go-to internet portfolio! You could make it a resume of all your best movies/art/contributions!
Sorting your favorite artists really becomes unmanageable as soon as you hit like 100+ favorites. It really isn't worth it at that point. What might be cool instead (and you may have touched on this?) would be the ability to "Crown" certain users that you want highlighter in your feed. Maybe their content stays stickied in your feed until you view it? If there are a few users that you absolutely don't want to miss!