It sadly can't. Regex paths are hard due to the way it's implemented; if it was intercepting syscalls via ptrace then regex would be a lot more viable, but since this is just a glorified collection of bind mounts in the end, I'm unsure how I'd implement that nicely...
Okay understood. Consider adding a way to query all files written by a boxed application. If it generated a config file based on this info that would be super useful. Thanks for considering!