If you can use a 10g tank for the sump, LMK and we can get you a new 10g tank to do whatever you want with. You can add baffles to chamberize the skimmer and return pump. Not a whole lot of room to work with in a 10g tank, but since it's all laid out in an enclosed area, you can easily get baffles cut and silicone them in place. This would be one of the easiest jobs I could think of.