It's simple to set a property in an Info.plist file from a user defined setting, you just use ${YOUR_SETTING_NAME} as the value. However, is it possible to do this for a bolean property? The structure in the plist file for a boolean is:
<key>NSAppleScriptEnabled</key>
<false/>
It's not clear how to use a user defined setting here.
I'm not sure how to do what you're asking, but I'm pretty sure that for this particular key (NSAppleScriptEnabled) you can also use strings "YES" and "NO" and it will work.