To create a backdoor, you could not be obvious. Like do something obviously evil in the driver... You'd build it out of many building blocks in several componen

To create a backdoor, you could not be obvious. Like do something obviously evil in the driver... You'd build it out of many building blocks in several components that individually look like honest mistakes. "Mistakes" that can be combined to create something malicious. That's what you need to achieve plausible deniability. You'll need to make it look innocent. (I also write Windows kernel mode drivers.)