I would add small rocks where the water dumps in, may add a filter sock to the hose to catch garbage. Also may put some eggcrate in there for your cotton pad. Take out the bio-balls put the skimmer there add sand to the sump add light. Good Luck hope this gives you an ideal or someone else can add to this.
edit:I just noticed if you can hang your skimmer on the back do that and still get rid of the bio-balls and replace that with sump rock.