Yeah sumps come in all shapes and sizes, well not all shapes but sizes. If you can find NOVA PRO's do it they are some of the best and they arent being made anymore.
Id just put the sump behind the tank, maybe move it to a corner and put it on an angle. its not wasted space behind there and gives you ample room to do things both above,under,front and back. I keep a torch lamp behind the sump behind my tank just cause I didnt want the wife to win the argument on space.
Heck 15g of water on the floor is scary I couldnt imagine 55 or if my 210 ruptured.
That's not a planted tank. That's a jungle with glass around it- MFDROOKIE Circa 2011