Hey Jamie,
I attempted this solution as well, but one thing I got stuck on was if I changed the parameter type to a Number, I could not use a "*" as the default value. It's a small thing, but our users are used to selecting "*" to select all options and it doesn't appear this method would allow for that.
Is there a way around that? Just don't want to complicate things for users who are used to things being a certain way.