Dude, have you never ever heard of people working on their fucking cars? Are you that stupid, or do you just play one on Slashdot? WTF?!
The ECM settings that can be changed without breaking the warranty are the ones that are there to be changed to begin with, pretty much. You really must have not ever worked on your own car using factory software. I've been working on my Volvos for more than a decade now and no, the factory software doesn't let you change the engine tune, or really do anything but what the dealer might be willing to do if you ask them. Yes, even the fucking dealer sometimes has advisors or techs stubborn or not giving a fuck enough not to bother changing settings (at an hourly rate!) that the fucking factory documentation advises specifically are changeable per user preferences. These settings are hidden only to route some more business to the dealer, BTW, there's no technical reason why they shouldn't be exposed to the user.
The seatbelt chimes as they are implemented in most cars on US market are useless. Either give me Swedish system where the chime is ON until you put the damn seatbelts on, or give me no fucking chime. In the US you normally have a chime that'll bother you for a few seconds then turn off no matter what you do. Worse yet, if your order of operations is start the car then put the belts on, as plenty of people do, the stupid chime will always beep at you for no reason other than some designer's stupidity.
The "shitty world of liability" is the one you live in. It's all in your head, a made-up problem. My close family is a bunch of litigation lawyers and even they aren't as risk averse as you seem to be.