Allow any field(s) in a group to be required

I had an idea for a new feature for CCK/Webform, but figured this'd be the best place for it...
I'd like to be able to assign some fields to a fieldgroup, but make only one of them required, and not a specific one.

Example: You want users to fill in a form and leave either their phone number or email address. You add both fields to a fieldgroup and set the fieldgroup to have 1 required value. This would mean that users can enter either a phone number or an email address (or both), but if they don't enter anything in either field, the form won't submit.

Actually, thinking about it some more, maybe it'd be better to make a separate group specifically for grouping fields that only need one to be required. That might be better than a fieldgroup that displays with a border, etc.

Apologies if this is already a feature (request); I've only tried the demo and couldn't find anything already in the issue queue...