RE: 2M Electric only planes...?
The Neu F3A-1 is 125mm long, not counting the prop thrust washer (back of motor can to face of gearbox/c clip).
I wouldn't mind an open bay construction. It should be light, no reason to overbuild these things. Heck, you could scale up the old Jumping Jack and have a neat plane.
I'd really like to see someone utilize a construction of subframe with thin molded depron skin. The skin of the plane does not have to provide the structural strength, it can just be aerodynamic. I would try and make the fuselage a CF tube (or long triangular shaft) and put ribs/standoffs on it to hold the other structural elements (tailfeathers and wing tube mount) and then wrap a skin around it. Depron skins (or thin vacu formed or molded skins) could be replaced if damaged. Heck, they could even be pre-painted.
All that has been done so far is to make electric conversions of glow planes. Sure, there have been some electric only setups, but they are not taking full advantage of what is possible and they are baby steps towards an electric only construction.
None of the planes listed in this thread are departures from the norm. I guess the Amethyst and Miss Wind Bipe are closest, but they are still using classic design and construction techniques.
Let's try some new ideas. I'd give it a go.