The essence of the question is:
"Is Nexus 7 truly unbrickable (without touching hardware)?"
The question is important (for obvious reasons), and not rhetorical (for reasons even more obvious).
So, what's wrong?
Or should I ask a dozen questions first, starting with:
"Nexus 7: what a bootloader is and how does it differ from boot?"
-- and then try to figure it out myself?
Heck, isn't this a "Q&A site"??