What you are asking is basically to switch to a rolling cycle with guaranteed support. This is a huge change and also don't account for the fact that many people choose Debian stable specifically because of it's non-rolling cycle...
* It's generally unpleasant for a user to know their problem has been fixed but they don't get access to the fix in a long time.
* Users using old software when they don't need to has network effects that give rise to negative externalities. See my other top-level reply: https://news.ycombinator.com/item?id=14580042
> don't account for the fact that many people choose Debian stable specifically because of it's non-rolling cycle
My suggestion is based on the premise that there are users who choose or would like to choose Debian because of its community distro brand equity and not because Debian stable has old software. Also note that I suggested a change in the framing of testing and didn't suggest stable be dropped.
But "have you spent the time evaluating it?" is beside the point. My point is that it would be positive to have a Debian release channel with fresh software with 1) explicit security support and 2) naming with positive connotations so that fewer people who don't need to use out-of-date "stable" used "stable" because it is the Debian release channel with the most positive-connotation name.
Asking each user individually to go against the framing of negative-connotation naming ("testing", "unstable") to get empirical data of what the actual level of breakage is wasteful. If "unstable" works so well, it shouldn't be called "unstable". Calling it "unstable" but telling people it's the solution to whatever is wrong with "stable" is a set-up for a blame-the-user excuse if something goes wrong.