You can now download an official package of GtkRadiant 1.6.7 binaries for Windows, with the new support for Quake II: Remastered.
Please see my previous post for details. This build comes with a few additional fixes, and a new github repository for the Q2RePack.
The entities.def in the pack is probably a little outdated, a conversion effort from the latest fgd may be needed (or directly adding fgd support to radiant).