So, more than likely, my easiest, most cost effective, fastest way to get back in the air with what I have is to probably make a champ out of my DT foam I already have? That way, it's literally swapping electronics from plane to plane?
Pretty much. You already have a template to build from and the other directions you can take either require something else (new radio or parts) or some trial and error (new airframe design).
Getting back in the air is pretty important to me so I won't try to stop you, but as you build the new airframe, try to build it so the electronics can be pulled out easily. That way, after you're done flying and your batteries are recharging, you can work on a RET delta to experiment with. When it's done, burn a battery on the new airframe and see what you like/hate, and tweak. Good chance you'll eventually make something you like better than the champ clone, and the brick stays in the scratchbuilt.