Some time ago, we had an IDM process that would use eDir groups to create distribution lists. What we found was that it led to tree-walking as a lot of users who would otherwise interact only with their local partition had to walk the eDirectory tree to be part of some large and diverse distribution lists that were kept in central partitions.
What might be useful is if a distribution list could be made up of the users from multiple eDirectory groups (i.e. act as a pseudo-nested group). That would provide a lot of flexibility on the eDir and GW sides of the house to properly structure the respective systems. However, in such a case the context of the objects should be preserved (i.e. if you have several eDirectory groups named "staff" in different containers).