I’m in the process of trying something like this. The cameras I bought have serial ports and firmware packages that can be reverse engineered. That’s where I’m currently at; just having the knowledge that it’s possible. I haven’t reverse engineered anything before, so if my attempts don’t work my backup plan is to harvest the the raw components and cobble together my own firmware on a different MCU.
Firmware in all the consumer devices I want to hack, but don’t want to reverse engineer.