Sigh. Look, I understand that you're not comfortable with people modifying stuff, but please understand that people designed it in the first place and that some of us are perfectly comfortable with entrusting our lives to our own creations / modifications. In fact, I feel rather more comfortable driving cars that I've worked on compared to those that I haven't worked on because I know those cars on a much more intimate level, both the good bits and the bad bits. And bad bits that you don't know about can cause surprises. One of the minis I rebuilt had completely rusted out sides, you could see the pavement with far too much clarity after cleaning out the rust:

http://pics.ww.com/v/jacques/cars/minis/greeni+1993mini/0529...

One day in Canada a mechanic in a car alignment shop that I won't name here told me that my left front wheel could not be aligned. I immediately jumped into the pit and started looking at the main components of the drivetrain and sure enough the left front diff was cracked all along its length.

Note that this guy was a professional that did alignments for a living and I'm nothing but an amateur. But at least I do know when and where to start looking for real trouble. A broken diff can seize up without warning (because all the lubricant will have run out) and can cause your neat Jeep Grand Cherokee to do cartwheels.

Working on car software is old hat to many, from increases in power (messing around with fuel injection tables) to fixing production issues that manufacturers never bothered to do recalls for to reverse engineering the software to be able to maintain older cars and to get them past emissions testing. Some of the people in the modding scene have absolutely awesome skills, on par with the best in the industry (and since they're working their way backwards from the designs in some ways more impressive).

All software has bugs, indeed, including the software that your vehicle came with in the first place.

If you mess with the charge curves on your batteries then you'll likely reap what you sow (I'd stay the hell away from there), but if it does overheat or explodes that will be just the same overheating or explosion that you could expect in a regular accident. Likely your EV has been designed around such failures, if it hasn't then you're in trouble even if you don't mod it.

If the brakes stop working then you're in trouble (and so is everybody within striking distance), but brakes failing due to a software bug that you induced is a thing that I've yet to come across. Most brake systems have mechanical back-up, and if all that fails you can still reach for the 'oh-shit' lever, aka the emergency brake. Anybody that has ever had a master cylinder fail on them knows what I mean.

Insurance companies deal in statistics. If you register your vehicle by brand and type then they'll quote you a value. If you plan on doing experiments with the drive train, if you increase the stock power by more than 20%, if you start messing with the structural components of the car (which I think is far scarier than any software mod) then there are procedures on how to deal with that. In some countries insurance companies will insure anything that moves, in others you need to go through a complex formalized procedure that tries to ascertain whether or not your car is fit for the road.

As with everything you mess with: know what you are doing and err on the side of caution, especially when lives are involved. But don't let that stop you from learning skills and applying those skills to real world hardware. After all, if everybody would stick to theory we'd never have a lot of nice things.