It comes up frequently with organizations I work with that when they start working with approvals they need an easier way to manage the voting and non voting members of committees. I.E. Loan Committees for financial institutions; with some members of whom present loans and others who vote on them.
If you have a committee that includes voting and non voting members you should make two user groups in the directory. One that includes everyone in the committee and one that only includes voting members. IE Lending Committee & Lending Committee (Voting)
This makes it much easier to invite the primary group to a meeting and invite just the voters to approval actions.