To be able to have an approver be on multiple levels or in multiple groups

Currently today we are only allowed to have an approver be in one group and or level. This causes us to have multiple logins for users and is horribly inefficient. It is also killing us as Staples has this ability and makes us look not with the times. We are wanting to be able to have an approver be part of multiple groups or levels. Use case is backups for other groups and not having to have 3+ logins as we do now to make the same thing work. New customers just look at us like we are not competent when we suggest the multiple users.