R Scott

Any diesel generator is rare in the US, with the current EPA rules you probably won't find one ready to go out of the box.

Make sure you're not spending a dollar to save a dime. Yes, tires are free but will hold 2-3x more concrete as a properly sized sonotube.

DEFINITELY use a bought post base. They include a spacer to let the post dry through the end grain and hold the post DOWN so a hurricane doesn't pick up your house.  

That uplift protection is what is missing in your original design.

Your rubble piers should work to a point, but I wouldn't go too high. Not sure how to easily add hold down pins and bracing to them. They would be great for a shipping container where you aren't worried about lift.

It depends.  Off contour helps if you have definite ridges and valleys that stay dryer and wetter.  On contour swales are an easy way to retain water in micro ponds and grow trees.  BUT either one can be done right or wrong for your land and weather and goals.  I agree with Rob 1000%

Muck now makes a wide calf version!

And their Edgewater model is pretty low heel, not quite zero but close.

I tried insulation over a tent without much success, too many leaks.  Hard sheet insulation works, but $$$. Two layers of plastic with an air gap or blankets hung inside with LOTS of safety pins to seal the joints worked best for us.  The thin painters tarp is cheap and comes in a ton of sizes.

Don't use the cheap blue tarps, the color will get to you eventually.  White or clear.

Whatever you do, plan on rodents and how to control them.  Hay bales, bundles of clothing, food, books-they will get everywhere in a barn.  They will get into Rubbermaid, anything you want to keep needs to be in a sealed 5 gallon bucket or better.  55 gallon drums with clamp on lids are the best I found for the money.

The billboard tarps get very stiff in the cold and are pretty dark.  I would use painters drop cloth plastic or cotton. Buy a few ten foot 2x4 to go between the trusses and a staple gun.

I did the plastic tarp carport.  Works great in mild weather.  Too much space in cold weather, added a bed tent to cut down the space to keep warm at night.  Electric mattress pads are wonderful, partners and dogs are better. Any other heat source is worrisome.

Another possible option is something like these: https://www.amazon.com/Tingley-35121-WorkBrutes-10-Inch-Overshoe/dp/B000BQPXOG/ref=pd_aw_fbte_3/140-1037992-4340458?_encoding=UTF8&pd_rd_i=B000BQPXOG&pd_rd_r=4bc79e49-f2ca-43e2-bf48-02f285186a80&pd_rd_w=pYrBe&pd_rd_wg=Apd3O&pf_rd_p=16a91b47-29f0-44ad-9cd6-3a1b8bcc4fa6&pf_rd_r=9MXG4GJ4CWQEZ36E31DX&psc=1&refRID=9MXG4GJ4CWQEZ36E31DX

They are thin and made to go over dress shoes.  Not a perfect zero rise, but if you trimmed an insole from something else they might be close.  The more expensive versions used to be natural rubber, but probably not anymore.

Another option is the boots made of crocs material.  Several brands, seem to be available at most farm stores around here anyway.  Not zero rise, but LIGHT and flexible.

Gabion baskets are common here, cattle panel or chunk of woven wire tied in a similar circle and filled with rocks the plow finds in the field.  Wire stretched tight between them and maybe a spacer standing in between-basically a cheap post resting on the ground with the wires tied off.