Thanks for the suggestion. My original thinking was that fields like this wouldn't make sense because they wouldn't do anything on their own -- and as long as you'd have to modify the code, you could add your own field. But I have come across a few cases where something like this would come in handy (along the lines of your example) and I am beginning to see how it would be useful to build this out so that you wouldn't need to muck around with the database schema, controller, add/edit dialog, etc.

I am hoping to implement a bunch of new features in the next few weeks and I'll definitely think about adding something like this.

-Jordan