Makes sense, but I'd have to get heaters or a controller with an automatic shutoff feature; the whole reason for isolating the return pump from everything else is to make it impossible for the tank to flood even if all the drains clog, and preventing the biomedia from running dry.I'd loose the baffle between e&f and make them 1 chamber. Put your heaters in this chamber, if you have a controller for the elements put the thermometer in the d chamber. That way your heaters and what controls them are the farthest apart, better heating that way. So when the water is at the thermometer it's at its coldest.
So maybe move the D-E baffle forwards 2", put the heating elements on that and have the temperature probe at the far end? I wanted a bubble trap there because the air pump for the biomedia chamber is going to introduce a lot of bubbles I imagine, but I suppose those aren't the problematic sort of micro bubbles to be worried about. That would add even more room for equipment in the chamber, but I'm already not entirely sure what I'm going to put in there.
Probably some stuff for nutrient export because the biomedia I have is already capable of removing more waste than my fish could possibly produce.