I would make a political-economical mod that make 1. For the political part I will overhaul the Pop and political faction system to be the sole actors of Stellaris (gestalt's empire will have a main actor and subordinate entities with various decree of autonomy). As a player you will no longer play a nation as it is but a political faction in your nation that play like the actual federation. Your civics and origine will not be plain modifiers ; they will have a direct impact on your nation and each autorities will have a unique playstyle associted with them.

1. For the economical part I will add a macromanagement focus that was despairingly needed since 1.0. Notably I will add the possibility to design your planets and create an economical plan to build your economy. I will overhaul the science and unity system; for science I will take inspiration from Distant Worlds: Universe and for the unity I will made them the national version of the federation cohesion's mechanics. The economic will be subordinated to the political gameplay of stellaris.