This is a step in the right direction. Something similar has been discussed for a while, with an additional element: The live version of the page is replaced *automatically* with the temporary version after a set period of time without edits.
As pointed out by the e-mail you linked, the timer part would be not-so-easy, even if I think it may be a good idea.
Your current implementation has the drawback that it might become very popular soon, even on pages where we otherwise try to avoid protection, and give sysops too much editorial responsibility.
IMHO sysops should be thought as reasonable people, so it shouldn't be difficult to dissuade them from abusing of the feature.
Regards, Salvatore