Hi Charles,
Hmmm, 500 mm would be about minimum for any of the earth plasters, and as Chris M, has stated may not be your best 1st choice. Lime may work, yet I am reluctant to suggest it as there are skill set that may take more time to acquire that you have of want. So that leaves:
Wood
This is a great first choices for many reasons.
One, if done well, and with traditional attachment modalities (like it being "rain screened") will last upwards of a century, which is more than competitive with aluminum and yicky vinyl siding.
Takes natural finishes that are relatively easy to apply and/or make yourself.
Flexible in design, i.e. shingle, board, plank-slab, live edge, etc. etc.
Can be done without nails (or few) panelized, and many other positives to function, form, aesthetic, and survivability.
Stone
This is also a great choice and can be used with a wood siding as in a wainscot style.
Durability is in the centuries.
Cost can vary widely depending on your sweat equity and whether it is salvage or not.
Alternative
This can be a real long list.
The first few that comes to mind:
Recycled large 1 gal tin cans cut, flattened and hung as shingle. There iron patina oiled with tung or
flax oil is beautiful. Sorce at recycling center, or commercial restaurants, etc. Takes about 3 months to a year to source the average size house.
Felt carpet padding, cut into shingle size, treated with additional fire retardant (as
should the wood.) This can be left "as is", painted with natural paint, and/or oiled. This can last a very long time (I know of some exposed to U.V. and ground contact degradation that has moss growing on it that is over 20 years old and still going (growing) strong. It is a marvelous product to take out of the waste steam, and one that many carpet companies would be glad not to pay to get rid off. Only issue is once I have told folks about it, the sources dry up fast, as every one wants it. It has 1001 uses that make it a high demand item.
Insulation
You can use foam, but I would stay away from it as it does not let the wall matrix "breath" properly. Homes need to be draft proof, (think good wool sweater) not "air tight" think tyvek painters suit or gortex...and we all know what those are like after just being in them a short while. Dry on the outside...clammy, dant and wet on the inside. Great concept...that doesn't work as well as hope in most applications.
Mineral wool board would be my first "man made" insulation, and then this is covered by a "rain screen" grid to hang the siding.
Hope that helps and gets your "juices" of creativity going...
Regards,
j