remember Afghanistan? There's no "finish the regime quickly". These are religious fanatics. See Taliban.
A bad deal will just give a short break before Israel and US strike a third time.
well unfortunately its survival would mean tighter control of iranian populace: it now has an excuse to do so ("are you an american spy? why do you disobey higher command?")
iran will become more like north korea more than before...
as for the iranian people? well those guys could have been driving porsche like qataris people...
Iran is the way it is because the West has been ruthlessly exploiting their resources, undermining their government, and attacking them militarily for the last 100 years.
but at least I expected US to be more prepared than this