It's a concept we've thought about doing for a while, Slornie and I especially, we've just never been sure what units we'd need. We've had a few people request it, too.
i think both the rebels and empire would mostly be how they are already in era 1, its just a matter of organizing them for the era system.
it would make sense to emphasize the differences in strength, where rebels dont even have cap ship building capability in the first era for example.
a third era is possible if you wanted to do pre death star > death star i > death star ii, which could fully document the beginning of the rebellion to the establishment of the new republic,
it might be fun to have the pre death star era on a timer and the rebels have to establish themselves the best they can in order to mount a defense when the death star is built and the second era is triggered