v0.1 of the PortraitPackEditor is linked in top post. Of note, it scans things alphabetically. Could move all existing portraits into a _Rename subfolder under Portraits and Bodies, then they'll always be at the top of the list until renamed/moved.
It does impose it's own structuring to the name,
<races>\<genders>\<ages>\<hair colors> <Skin colors> <tit sizes> <ass sizes> <custom text> #.ext
The # starts at 1, then if there's already a file with the exact same name, it increments to 2, and so on till it finds one that isn't in use.
For the age selection, it is a bit of an issue, as no teens, right now means it falls back to everything. I don't think making it fall back to loli is the answer though. Partially depends on your definition for those.