Speeduino definitely a great start and is also a viable pathway to the same goal, I really love this! My idea is definitely not something developed, more of a light bulb moment, so there is definitely tons of considerations that are yet to be addressed. That said if the manufacturing becomes distributed and replaces certain parts to "jailbreak" the cars that would be a great start. Next phase would then be figuring out how to decentralize manufacturing at scale or at least empowering hobbyists to build their own much faster and easier