Observations on opening the new 21.5 inch iMac.
To open the new iMac, you've used a heat gun and guitar picks to get past the 'adhesive' holding the display down. You conclude that: "you'll have to masterfully peal off the old double-sided sticky tape and apply new tape in order to reseal this iMac back into original condition". Most think that the display is somehow glued to its aluminum case, and then must be re-glued after operating on the internals.
By carefully examining many of your photographs, as well as those of Kodawarisan and others, I suggest that the joining of the display to the case may really be some form of a simple micro Velcro fastener that can be released without destruction by heat or brutal force, and unnecessary joint replacement!
If it is indeed a Velcro joint lining the sides and the top, but not the bottom of the display along the aluminum 'chin', then I suggest that the opening proceed as follows: the suction cup holders should be applied to the bottom square corners of the display, not the top rounded corners as is usually done. The force needed to open the case at the bottom is considerably less than if it were applied to the top rounded corners – this is because there is no Velcro lining along the bottom edge of the display. Note that in the magnetically attached displays there are no magnets along the bottom edge of the display. Similarly, the magnetic joints can be opened with much less force if the suction cup pullers are applied at the bottom instead of the top rounded corners. Finding a proper release of such a Velcro joint would greatly simplify the opening, and closing, of the iMacs.
I hope you carefully re-examine the tapes lining both the display and the case, and see if these could possibly be Velcro tapes. If these really are Velcro joints this is a simpler and better, and much cheaper way than using magnets. All it takes is to know how to properly open a Velcro joint. Maybe you will be able to put away your heat gun, guitar picks,and replacement tapes for future iMacs!