That axle pad is a good idea ... EXCEPT I'll bet my E450 rear axle tube is more than 2.5 inches in diameter! What about jacking on the bottom leaf spring instead of the axle tube? Remember that the further you go inwards to jack the more that has to be lifted and the more instable the lift becomes. You should keep the jacking point out as far from the differential and as close as possible to the inner rear tire as possible - hence lifting on the bottom leaf spring instead of the axle.
Another concern is what to put under the jack's base so it's not forced down into the earth instead of the RV's axle going up? I carry several leveling blocks that can also be used under the jack's base. The hydraulic bottle jack I carry also has an extra tall lift (dual stage) in case the jack has to do it's thing in a slight ditch or road rut. I also carry a full size shovel along!
We have a long range cell phone system in our RV to help contact ERS when out of normal cell tower range. However, we go off paved roads out into the desert, so I sure wish that there were an ERS service available with 4X4 550/650 series trucks that would help you just about "anywhere" ... I'd of course pay a premium for the peace of mind that this type of service would provide. How well does that flat-repair-in-a-can work on the larger tires that RVs have on them? I know they work on sedans/SUVs .... but how about on truck tires?
For what it would be worth, we also carry along a 120V AC full pressure compressor that the built-in generator can run.
Now ... getting that full size and full weight spare tire and wheel dropped down from the E450's frame in the back and pulled out could be a whole nuther problem. I'd have to just put the flat tire inside the motorhome on the floor after I changed it.
I do run with full pressure in the rear duals so that I can limp along very slow for some ways on the one remaining and over-loaded tire in a rear duel set. This can be done carefully - and I have done it. The tire I over-loaded lasted for another 20,000 miles or so, too.
ERS is nice ... but it shouldn't be relied upon solely for certain camping styles. After all, the whole point of "camping" for some of us is to be where people aren't normally living at.