A clan could have a "trusted" list...set by the owner only, to allow auto-accept or auto-reject (if room exists) of certain players. There could also be "auto admin". This would be nice for those times when people leave to go to a subclan and come back only to find no admins are available to let them in the door. There could also be a "banned" list of people who cannot apply and are automatically rejected. This is especially helpful in cases where someone might spam-apply to annoy a clan's admins.
I think the coding on this would be an absolute pain - so I'd start with just adding an "Auto-accept" feature and work from there.