You obviously have never taken an iMac to pieces... no way is that "chin" going to disappear fast.
All you stuff is mere fantasy but for Thunderbolt which will mean fluck all to most people
Pretty sure the "chin" houses fans that push the heat to the slit in the top. Heat rises...makes sense. That, and I've heard..."the fans in the bottom of the 27 inch will keep that ***** cool when you're pushing [insert Creative Suite program name here] to the limit". Three fans in the 27 inch one in the 21 inch.
What's funny...last year, I was stoked to get an iMac...I had the cash ready...and literally...that same day, moments before I checked out with my costly machine...the new iMacs dropped. I quickly decided to hold off on buying. I've been computer-less since, but I like to see it as an exercise in self control.