Great idea.
Few suggestions/ideas:
i) How long would the server last? Personally, i would prefer a 5-6 days running over the weekend. Alot of players have RL issues to deal with and the weekend would allow all to concentrate on playing, also might entice the older players out of retirement.
ii) Have two of the listed players per tribe with each set at a maximum of 15 players. This way we can establish at least 10 uber tribes and share the workload.
iii) Agree with Le Roi 1980 on NAPs/Allies or doing away with them all together.
iv) S/M is optional and only members of your own tribe can sit. Tribes are locked after "xx" and you are only allowed to support your own tribesmen.
v) Players are positioned randomly on the map. At the moment we are allowed to choose where we want to start. Random would stop players clustering in packs of 2-4 on each continent...and add to the fun.
vi) No "ringers". Everyone must play under the login they are commonly known as.
) Allow a SDS tribe to participate (if they haven't already been considered)
HAve a few more ideas, but have mind block. I'll post them later on.