I'll begin by requesting a Senate Leader Selection Mod
Being able to arbitrarily change the leader might not be as immersive as some complex hero-duelling player-induced event/quest, but it would be better than what we have now.
Especially diminished by the current system are the mods which add new heroes and or faction traits for starting with additional ones

What about a mod where you can choose which planetary anomaly you want? It gets a bit tedious having to constantly start new games just to be able to get the setup that you want

I'm hoping for a Battlefleet Gothic, or a Warhamer 40k mod.. would work perfectly for this game..... wonder if they would be able to show ramming mechanics when watching a battle.

How about a state propaganda mod?

Basically to introduce an option similar to the "convert 25% of production to dust/science" - instead it'll be "convert production into propaganda, convert 1 citizen in the given system to political party X per 200 production spent"

I need this so bad in the game

Faction trait curiousities: there are very rare curiousities that grant a random positive faction trait for the player that discovers it, possibly replacing an existing one with a greater one (for Sophons and Horatio, it may give a negative faction trait that replaces the original one with the lesser one: Feeble warrior I for Sophons & The Price of Beauty I for Horatio).

Simultaneous completion of Legendary Deeds: some deeds can be completed by more than one empire simultaneously, such as construction of wonders. If multiple empires complete the same wonder at the same time, the bonus it provides is divided by the number of empires that completed it (other empires will be unable to build it). If a legendary deed that awards resources (luxuries, strategics, influence, science, and dust) is completed by multiple empires simultaneously, the rewards are divided among those empires that qualify.

New government types: Anarchy and hive. Neither is available in the custom race menu, but they should be. Anarchy should be designed around not being able to use laws and hive should be balanced against the impossibility of rebellion.

I loved this mod( http://www.moddb.com/mods/endless-effect ) for ES1 even when it was never finished.
I wish something like this for ES2, maybe not Mass Effect conversion but Star Wars or Halo,... would definetly be cool.

Also, the more I play this game, the angrier I get that buyout prices are all insanely high. I can't get any use out of Emporer's Will to buy techs, to start with. They're all literaly impossible to afford until so few turns are left that there's no point in accelerating the process. And I'm using a modded custom race with influence bonuses that aren't available in the vanilla game.

It's also pointlessly expensive to buy things with dust, to almost the same extent as influence. The AI won't trade in it, even if they're offered thousands for a few dozen resources of a single type. I can't find any resource that's balanced for actual trade, sale, etc. no matter how long I play the game. And there's not one mod that fixes it anywhere on the Workshop, so I'm requesting it here. I'm sure this is the type of thing that should be fixed in a patch. I'm also sure that the developers can't screw up so much of the fundamental trade balance this badly without an agenda, so that patch is probably never coming.

(Edit: partially retracted. Trade balance was considerably improved in a recent patch, and may be completely fixed one day without modder intervention.)

I wonder if it is possible to combine two affinities like because i like the vaulters's metaspace to teleport your fleet from one end to another but i prefer emperor's will because they can buyout things using influence. and i am stuck between the two....so can anyone mod them together to make that happen or at least be able to pick which other affinity you want to combine?

Just an idea I'd really like to see... A custom trait that gives you the ability to Brainwash instead of Assimilate, without having to have the Shipbound affinity(could even allow brainwashing of systems outside network for Celestial Vines factions). They could give you resources from their system instead of Essence.

And maybe another one that prevents building of Colonization ships(incompatible with Shipbound, Celestial Vines, Planet Brokers and Involuntary Nomads, for obvious reasons) and has negative cost since it's a downside trait. (Yes, I'm trying to put together a Cultist faction.)