if you want a stock theme, just reinstall the gapps-update.zip
they aren't doing a stock theme anymore, since the gapps update reverts to the stock frameworks (i'd assume)
Actually, the framework isn't included in the gapps update.zip, so you would have to install the rom too. Bgill is responsible for theme related things, hence the name the Jeweler, so he has a lot to do with things like this.
you're right, you'd apply the rom and gapp without wiping... theme would revert to stock without messing much up.... either way the story is the same... no more stock theme in a zip to install over a custom theme.
from the wiki
""With this release, we have done away with the “stock” theme in favor of just re-applying the provided update/gapp update without wiping data""
If Bgill doesn't set one up for each release, I will then. I feel that reapplying the whole rom to be quite annoying. I like having one small zip that covers what everyone themes. I am sure bgill wouldn't mind making one either.