I've been having the same debate. I was up in the Yukon / Alaska where most roads are "off road"...but having an FJ wasn't the answer as its a TANK on gas - and had no flat area to sleep when camping.
I took my E into a mechanic in Boulder, Colorado who mainly does mufflers, we talked about remodeling the muffler as it hangs WAY too low and has 3 canisters that are much too vulnerable. I would have done this, along with the 3" lift kit, but the issue of a plastic low hanging gas tank in the middle of the E still remained. We considered a metal sheet as discussed in this forum, but really, the gas tank is too far centered and way too low.
Has anyone considered re-locating the gas tank? Would it be possible to relocate it into the spare tire area? I currently use this area for tools, bike gear, etc and have a Full spare tire in my roof rack, with a 10L gas can.
With a new tighter muffler system (with a 2 & 1/4" pipe which allows the E to breathe better = 1-2 mpg better), and a re-located gas tank, the E would have a ground clearance of 9"! Add the 3" lift kit, and we have a 4 cylinder truck! Its no FJ for off-roading, but I'm not crawling on rocks, I just want to get through the next creek without losing half of the E
Any thoughts on relocating the gas tank?