[Xietor]

Well,

for the advanced player, you may want to play a MA race, and add some EA or LA empires to create more of a challenge. It would be an option, not a requirement.

So you play MA Pangaea, create a map and random opponents, and they will default be all MA races.

But, for those wishing more of a challenge, You can "select" empires from different eras to throw in as opponents for a greater challenge. So it would be completely optional. Also, you may have 1 player that is an "expert" and a friend who is a casual player, so you may want to let him/her play a tougher race to equalize things.

MOO2 had a race that was overpowered on large maps, that got to research every tree at once. Many times i would allow my friends to play this overpowered race, while I would play
a more limited race to balance out the game. There is nothing wrong in having some races be overpowered, as long
as it is intentional and everyone realizes that they exist to allow the more casual player to compete against more experienced players.

In Dom II, ermor was overpowered. And I often allowed a friend to play ermor while i played ulm or some other race.
It created an even game that would not have been possible if my friend would have played a race other than ermor.