More Unique Faction Gameplay Directions (ei: Mezari/Sheredyn shift)

The United Empire reach a point in time with their main questline which allows the player to make some large decisioins that will affect the stats of the Imperials race in the empire. The choice between either Mezari or Sheredyn ultimately allows a stronger transition from the standard Imperials to one that might better suit the gameplay decisions or direction you wish to go.

While adding those copy and past to other factions would be "boring" there are some unique ways you can add this kind of important decision making gameplay to other factions.  The Sophons in particular could be given such choices as you could either keep the traditional Science bonuses or shift into the Mavros style with militaristic/industrial gameplay. Rather than simple quest which would change all existing Sophons to Mavros like Imperials > Mezari/Sheredyn, you could create a more subtle shift. Maybe existing Sophons remain Science focuses but new populations become Mavros or you could gain access to a new Development named Mavros Academy which when constructed would make all new Sophon's gained into Mavros or all in the system. 

While you get some unqiue Developments from quests non feel as powerful or game changing as the Mezari/Sheredyn transition. Other than population stat cahnge, you could also introduce a development that has a substantial effect on how that faction feels.

This kind of subtle shift to the existing faction archetypes could increase the players personal attachment and experience with the the faction in each game. Each divergent outcome doesn't need to have large gameplay ramifications like with the United Empire's choices. These could easily be added to a couple of the existing factions without large balancing efforts needed.

TL:DR

UE have Imperials => Mezari/Sheredyn

New options to slightly change faction:

Sophons Can slightly shift more towards Mavros Industrialists.

Riftborn lose some portion of stats and gain some Influence/Manpower/Food stat.

Unfallen get anything other than pure food. 

Unfallen Possibly gain new vine entwining system that makes them entwine from a system away for more aggressive moves or maybe they can charge up a vine ship and build up a charge to be instantly deployed to create greater more interesting late game movement.