For someone running a closed loop system your idea wouldnt work to well, You couldnt control the flow rate to make it work right. I think your idea is great but for large set up running large return pumps their is no easy way to get around the flow rate. If i had a natural filteration set up and no large return pumps I would be all over this idea but I do and I cant.
Now please dont think I'm saying your idea isnt good because it is, just not usable for all set ups.
150 rr Oceanic, 300 pound lr
,250 pounds ls
's, polyp's,soft corals, sps