as long as the ecu allows u to start ur car even when changing the radio or tinkering with the infotainement system i wouldn't mind..but i probably doubt it: car manufacturers will really tie critical car features to spying hardware so they could reach their end. yea, an older car is the best answer for this. also ecu firmwares and sensors and car parts needd to be open sourced somehow

yea man buy an old car and riddle it with fancy features: (TPMS):tire monitoring pressure system, Lidar for brake anticipation and also highway cruising, parking sensors and cameras back and front, dashcams front and back (even cameras at the door handles like a Tesla). Tbh i like it when an old car gets modded by third party with latest car features that way u really saving the environment from a ton of metal junk. A BMW or A Tesla are just filled to the brim with sensors, but also more parts mean more breaking parts so there should be a balance between refurbishing an old car and making it basically undriveable with breakdowns.