Feature request: ability to set minimum subscription levels

Would it be possible to add an option on the backend that allows me to set the minimum subscription level for all groups?

For example, I have a group that I require members to receive at the very least a weekly digest, so I would very much like to be able to say that, for that group, members are prevented from selecting No Email.

Cheers

http://wordpress.org/extend/plugins/buddypress-group-email-subscription/