Problem: Hard Drive
The main problem is, that on a sudden powerdown some changes might be made to the hard drive, that are not welcome (e.g. an important write operation is interrupted or the read head hits the disk). So the main problems with a poweroutage is the disk.
Software solution: "Frozen system"
Once I read about a "frozen system" that was loaded form hdd into ram. Then the hdd was unmounted. This way the hdd will not get damaged by a power outage. The downside is, that no changes that are made to the ram booted system will persist.
I tried to find the article about that, but was out of luck so far. If this sounds like a solution for you, let us know. Maybe we can do something similar from scratch.
There are also hardware solutions to the problem. A battery based system, that stores just enough power for the computer to shut down properly. There are commercial solutions for this available that cost about 200$. If you are well versed in electronics this could be build quietly cheaply using a few old car batteries, a battery charger, a few relays, a micro controller chip and a few other couple-o'cent-components.