The main problem with dehydration as I understand it is similar to that of cryopreservation, but worse: dehydration causes cells to shrink which damages organs. It also concentrates cellular components (salts, proteins, etc.) to the point where they start interacting with each other harmfully.
That said, it's an interesting starting point. Mike Darwin has proposed replacing cellular water with some kind of solvent carrying monomers that form a hard polymer under controlled conditions, possibly similar to Amber. Once it polymerizes and forms a glass, the cell's components would be unable to interact with each other. (The organism would be cooled to -20C using M22 for cryoprotection beforehand to minimize metabolic damage.)
The hard thing is getting a high concentration of anything into cells without rupturing them. Organisms like Tardigrades that achieve cryptobiosis (= anhydrobiosis) manufacture their own polymers such as Trehalose. Plants do the same with Sucrose. Cells have a special transport protein that yanks glucose (the most common sugar monomer) inside through the lipid membrane very quickly relative to their natural diffusion rate. Note that this is useful for cryoprotection, not just against dehydration.
Lately I've been wondering if Foldit could be used to design proteins that pull other things into cells faster. Could such an enzyme be programmed to embed itself in the cell wall? Perhaps something more like a virus could do this. Or perhaps a custom protein could turn glucose into a more suitable polymer under the right conditions.
If you don't believe in an afterlife, then it seems you currently have two choices: cryonics or permanent death. Now, I don't believe that cryonics is pseudoscience, but it's still pretty poor odds (Robin Hanson uses an estimate of 5% here). Unfortunately, the alternative offers a chance of zero. I see five main concerns with current cryonic technology:
So I wonder if we can do better.
I recall reading of juvenile forms of amphibians in desert environments that could survive for decades of drought in a dormant form, reviving when water returned. One specimen had sat on a shelf in a research office for over a century (in Arizona, if I recall correctly) and was successfully revived. Note: no particular efforts were made to maintain this specimen: the dry local climate was sufficient. It was suggested at the time that this could make an alternative method of preserving organs. Now the advantages of this approach (which I refer to flippantly as "dryonics") is:
There is one big disadvantage of this approach, of course: no one knows how to do it (it's not entirely clear how the juvenile amphibians do it) or even if it would be possible in larger, more complex organisms. And, so far as I know, no one is working on it. But it would seem to offer a much better prospect than our current options, so I would suggest it worth investigating.
I am not a biologist, and I'm not sure where one would start developing such a technology. I frankly admit that I am sharing this in the hope that someone who does have an idea will run with it. If anyone knows of any work on these lines, or has an idea how to proceed, please send a comment or email. Or even if you have another alternative. Because right now, I don't consider our prospects good.
[Note: I am going on memory in this post; I really wish I could provide references, but there does not seem much activity along these lines that I can find. I'm not even sure what to call it: mummification? Probably too scary. Dehydration? Anyway feel free to add suggestions or link references.]