You can (pretty sure) override the name of a talent via localization files.
You can modify the effects of a talent that are configurable through Data.txt.
You can modify requirements of talents via Requirements.txt.
You can script additional effects to a character upon learning a talent, and remove these effects upon respec. This means that, for some talents, you can apply an effect that counteracts its own effect--essentially removing its default behavior.
Anything else, that still aims to preserve the talent UI, is not possible.
