Templates have so semblance of data, so without being passed in an already fetched set of users in $users, the system will not know what to do.
On top of that, the display output is unclear in your suggestion, but for something so broad, you would need to define the display anyways, which gets you basically back to a normal fetch, xen:foreach loop, and writing to display.
I, personally, do not see the merit of the tag your suggesting for the reasons I just stated.