Reducing the number of fonts available to specific applications?
There doesn't appear to be an easy solution. Here's the best I could come up with.


In Font Book, reduce the font set to the "minimal" set by disabling fonts as appropriate.
Create font "collection" folders in some directory of your choosing by symlinking to fonts in one of the font locations as appropriate.
On an app-by-app basis, within the application bundle:


Create a directory within the resources folder that symlinks to one of your "collections" folder
Add the ATSApplicationFontsPath to the info.plist file as appropriate.



Ideally there'd be a way to specify font collections rather than font folders, but it seems like Apple intends this to only be used with prepackaged fonts, not by the end user. If you're keen on using the Font Book GUI, you could read from the ~/Library/FontCollections folder and automate step 2. You could also take it a step further and automate step 3.