Wouldn't it be easier to use a modern linux/freebsd kernel with a lightweight userspace?
On top of that curves and chacha20 could be used for ssh to reduce the CPU load.
[1] https://webcache.googleusercontent.com/search?q=cache:frP4SG... (from cache as it doesn't seem to work right now)
Now, I'll say, after 30-40 batteries, I've never had one catch fire. I've had a few that I probably broke as a result of heat, and I suspect that if you've tested the cells carefully and the batteries are in good condition, that they tolerate the brief heating better than cells that are already damaged, but that's not something I'm willing to bet my shed or my body on.
In a typical "failed battery" there's rarely more than one dead cell in my experience. And I've had packs with as many as 9 cells.
From there, it's a matter of putting it all back together. There's soldering involved, and you have to be extremely careful -- hit the battery with the temp required to melt the solder for too long and you have a seriously dangerous situation on your hands. I use two 3D printed clips and alligator clamps to hold the wire, wand and battery at distance from one another, battery on the bottom, wand on the top, wire in-between, and a 120mm fan, requiring me to only hold the cable to the wand and the length of solder.
Can't caution enough that it's exceedingly dangerous soldering this kind of battery. I originally built the rig because I wanted to improve the quality of my soldering -- I'm pretty terrible with an iron, but I made several changes after I had a small number of batteries start failing after repair and a few searches led me to believe I may have damaged them[1] with my poor soldering skills. My rig involves two 3D printed clips, one to hold the iron exactly where I want it, and one to secure the battery. The cable to the iron has a length of wax lace on it to let me pull it back up/remove the iron from the rig with a yank at a distance.
I use an alligator clip to hold the wiring in place and a long length of solder so that I can stand an arms length away. The iron "drops" in -- it's mounted on top, battery on bottom, wire in-between -- so I can heat it up an inch or so from the battery, I place tip of the length of solder in its spot and "tap" the wire of the iron to drop it into place. When I see it melt the tip of the length of solder and the small amount that's on the wire, I pull up on the string to move the iron away, wait a few seconds so the 120mm fan can cool things a little, and put a new battery in.
Goggles, gloves and a nearby fire extinguisher of the right kind are a really good idea. I also do the work in a large, mostly empty, shed with doors that, when opened, eliminate nearly an entire wall and work directly on the cement floor.
A lot of devices use 18650s and not all 18650s are the same. The one powering your drill might be able to handle higher drain than the one that came out of your laptop; don't mix those up. I was given a cardboard box full of dead laptop battery packs from the same model, so I was taking cells from a similar source each time.
[0] I use an adapter that lets me power a Raspberry Pi via an 18650.
[1] And likely made them into a fire hazard on their own.
I'm fairly certain you meant your comment in jest, but figured it was worth pointing out.