I started cloning the original fedora 24 template, which is already
configured for the correct yum repositories, and upgraded that to 25.
Since the yum config is dynamically expanded to the actual distro
release number, it just works. I'm on Qubes R3.2, and I don't understand
both why the fedora 25 template is missing from the 3.2 repository and
why a user should wait for such a template to be available in the
repository, while he/she could just clone the 24 and update that, if
having a cutting-edge-stable system is important in their scenario
(like, in mine it is so I did just that).
If you start with a template from scratch you can either use the yum
repositories or the debian ones, depending on what your distribution
supports, or you can include a specific version of the tools you
compile/make yourself - the vast majority of them is in Python, so there
should be little trouble using them in another distro. If you do include
a specific version updates will likely have to be manually detected and
installed, unless you also set up a custom repository and package
manager system and maintain that.
--
Alex