There should be a subgroup within the microcontrollers category dedicated to the attiny series of microcontrollers, I just noticed that 50% of all posts in microcontrollers have to do with the attiny85. Would this be possible?
I would say a bad idea.
There are already too many groups to monitor - I use tabs to monitor a few; it would be a nightmare without, to say nothing of the ill behaviour of the forum software in general, the "token" bug and the present annoying bug in "Tab Mix Plus" new tab opening on Firefox.
The fact is, few of the Knowledgeable Ones confine themselves to ATtiny, so you propose asking them to monitor yet another group in addition. I may not have any present experience with such chips (at least until I score some cheap on eBay) and therefore (sensibly) do not contribute to those discussions, but if the topic looks interesting, may well take a peek.
And there is the point - it is hard enough educating newbies to write meaningful descriptions of their projects, let alone write a cogent "Subject"; asking them to accurately categorise according to chip introduces yet another hurdle. :D
I agree wholeheartedly with @Paul__B