it sounds workable, but i'd say put the gb above the ft, with the sump below the ft
pump from the sump into the gb,, which drains into the ft, bringing oxygenated water directly into the ft, which overflows into the sump
or go sumpless and pump from the ft to the gb
adding a small aerator isn't really going to add to complexity and will be good for the fish

you'll probably have some solids settling in the sump that should be fairly easy to siphon out as needed
and i'm sure others will chime in with ideas