ha! clever man with the lightswitch, it looks like it's coming together very well and looks quite durable
as far as mounting the ESC and receiver together, there should be no problem, the only issue I could see.. which is 1 in a 1000 chance... if you crashed and that part of your vehicle was the point of impact, you'd lose both the ESC and receiver, hahahaha, but at that point i think i'd just say, "you got me this time universe!"
the only reason I placed my ESC and receiver box on the right was to counter balance the weight of the battery. Really I think for you it's just personal preference and convenience. What I WOULD recommend is placing them together, in the case your chassis snaps in half and violently thrown in opposite directions, your wires from your servo and esc into the box aren't ripped apart.
So my suggestion is keeping your ESC and receiver box towards the rear so that your motor wires, esc wires, and receiver box will be safe and together.. and you'd only lose a $20 TRX2075 servo in the event of some violent crash that would separate the chassis in half since that is your weakest point
Mmm good points about a possible chassis break and keeping the components on the same part. But then considering how strong the chassis feels, if it comes to that there may not be too much left of it anyway...... :-)