Suggestion to overhaul war and diplomacy

[bernkastello]

Right now war in Stellaris isn't too deep. There is no option to join the ongoing war, no way to join a federation even if you are fighting on the same side and no way to intervene the war without having to declare the war yourself. There are plenty of ways how this system could be improved, mainly by introducing some mechanics from another paradox title, HOI4, like sending volunteers and attaches. What I suggest in particular:

1. Add a new diplomatic action, "Intervene into war", which would open a GUI with the list of wars targeted empire participates in and three options: "Send volunteers", which would allow you to choose a fleet that you want to send to a targeted empire, number of which would be limited to the percentage of fleet capacity you are using at the moment, "Share intel", which would give a targeted empire the intel you have on the enemy empires, "Send military advisors" which would add a modifier to targeted empire that would increase their ship experience gain and ship fire rate, while giving you intel on them. "Intervene into war" action should be limited to militarist ethic and/or Supremacy tradition tree. Empire which sent volunteers should control the ships, and if it's not possible due to mechanics of Stellaris, should hand them over to the targeted empire like mercenary fleets, with an option to either maintain them or make its ally deal with all expenditures. Empires at war with your ally should get a harsh opinion penalties based on the scale of your intervention, with worst appearing when you use all three intervention options simultaneously. Empires in which wars player intervened in should get large positive opinion modifiers based on the scale of intervention. Empires with the attitude lower than Neutral shouldn't accept the offer to intervene into war
2. Add an "Ongoing wars" tab to the Galactic community, which would show all the wars which involve Galactic community members, and add "Galactic statistics bureau" resolution to the Galactic institutions, which would allow to see precise pop numbers and increase trade willingless for all empires
3. Add an increase to volunteer forces cap while progressing in Mutual Defence resolution, and add a ban to interventions in Independent Tribunals resolution

All these options would allow a player to have a greater control over situation in the Galaxy, because he would be able to influence the outcomes of military conflicts while not required to start a full-scale war, gradually building his sphere of influence. They would provide a more immersive mid-late game Cold War-like experience, because because proxy wars are really enjoyable when handled properly