With Pro version most of the settings are "per level", so you can tune the plugin very fine to achieve your needs. These includes: limitations of email's domain for submembers, limitations by custom field's value (new one) and to demote or delete the submembers, when master is deleted.
With by custom field's value you can set a second restriction: by s2Member custom field. Means, all the members in the group of each master must have same "City" value, as example. Different masters can have different cities, but their groups will have only his master's city.
Another great feature with the Pro version: a master can have submembers in other level. Your masters at Gold level (per screenshot settings) will have 10 submembers at Bronze level. Moreover, the Bronze members (who may or may not be submembers of a Gold master) will have 5 submembers. So it is possible to have "domino effect" - when a Gold member expires, all his Bronze submembers expire too, and his submembers (sub-submembers to the Gold member) expire too, so the whole "tree of members" will go to the free level. And backward - when the Gold master upgrades his membership, all the submembers and sub-sub-...-members are set to his levels again. That's the real power of this plugin. Note, that this comes with a price - free level can not have submembers. Also you must not do "dead loop" of sub-membership. Be careful.
Hope this will do your life easer :-)