Imagine offering up your own brain (and probably life) for a beta alpha version of a prototype from a guy who's products have never left the beta stage?
As a software engineer myself there are certain things I know I never want to work on. Things like heart pumps and diagnostic machines where firmware needs to be so incredibly precise that one fuckup and people literally die. And these people trust the guy who makes Teslas. They're fun to drive... I wouldn't stick one in my brain though.