I think we mixing up the cakes here. One thing is unrest and another is morale. Low morale could lead to unrest while a specific event could leave to unrest regardless of the morale.
So I will keep this post within the unrest as it is in Aurora without adding anything else.
You have so much that could contribute to unrest in the way Aurora already considers it. I know some could agree with others on this post as they don't think something could be achieved while others would like to make it more interesting. Where I stand will be clear at the end of this post.
Back to the datas, you have at least 5 currently in game right now that could easily contribute in creating an equation able to satisfy many without destroying any mechanic or upset other players. Eventually such mechanic could be made optional through a check box same as the political reliability and realistic promotions.
2 out of 5 are already considered: Protection Value and Slavery (even if this could be objectively buffered a bit with more severe penalties at least).
I feel like while the current unrest mechanic could be a bit more robust, the current system is good in its simplicity. Specifically both are tied to definite causes in-game which the player can directly influence, and the player can approach the causes of unrest in a few different ways to handle them which interact well with the core game mechanics, plus to a certain extent encourage "realistic" play without limiting options. This is a hallmark of good design.
Then you have:
Unemployment - this is an objective cause of unrest unless you live in an utopia society where people receive a universal wage to basically exist.
This is a difficult one. For starters, usually at the start of the game there is a significant unemployed fraction of the population which can be grown into economically or used to found colonies without killing Earth's manufacturing efficiency. This would also be a rather limiting mechanic unless it was toned down so much as to be barely noticeable, since often one will found a colony and populate it well in advance of relocating industry, etc. in order to stay ahead of the ball, so to speak. Finally, in realism terms a certain amount of unemployment is healthy for an economy as it facilitates a balance between labor supply, labor demand, and movement of laborers throughout the economy. In this respect, a flat "unemployment == bad" approach is not realistic, whereas an approach based around (say) a target unemployment fraction would be I think too complex for a mechanic where simplicity is preferable.
Access to trade goods: a shortfall of certain trade goods should cause unrest. Now this is tricky as it also affects civilian companies and such, but again something that could be easily overcome with a little buff lowering requirements perhaps.
This would be horrible to me as a player, because I have little if any way to actually influence trade goods. Besides the fact that only CSLs move these goods, I don't have any direct control over how to produce them to maintain a balance. And frankly, I wouldn't want the ability to do so in the game, because giving the player a knob to jiggle which only has the purpose of preventing Bad Things™ from happening is poor game design. Gameplay is best when it allows the player to work for a positive achievement, and worst when it forces the player to work for the sole purpose of staving off a negative modifier.
Finally population. Same as per unemployment is unreasonable to think that in a society everybody is happy and a minimum of penalty should be applied regardless. Could even be 0.0001% per Mil pop for instance. Will require some testing of course but everything does.
I believe PPV already incorporates a population size effect, larger populations require more PPV, so this would be somewhat redundant. Currently the PPV mechanic works well because it allows the player to address the need via any combination of ships and garrisons which meet the net PPV/unrest reduction needs, thus is quite flexible. A redundant population-based unrest modifier forces the player to maintain larger garrisons on bigger colonies regardless of PPV, which rather eclipses the effectiveness of that mechanic.
The problem
While in theory all is fantastic and yes let's get more unrest and such there is a problem. At the end of the day all can be solved with more police, more Protection Value, and more and more you get the point.
So unless that can be sorted (and considering how the system is structured now I don't think you can) I don't see any reason why we should touch the system as it is right now. I mean all you are achieving is to build more ground units to counter the higher unrest penalty.
Spot-on analysis, except that PPV does not directly reduce unrest. Only ground units do this. Otherwise though completely correct, ultimately all we're accomplishing is forcing the player to station more ground units everywhere. Currently the unrest system encourages this, but does not require it, leaving the player with flexibility to decide how he places his colonial defenses.
Obviously this is my view and I am sure there are many good ideas ready to change my mind. But these ideas must actually introduce a whole new mechanic and I am sure it will be super interesting but I really would like to have independence to NPR directly or even monetary aids, exchange of ships and such back from VB6 first to be honest before looking into unrest and revolts.
Agreed.
Independence directly to NPR is chiefly limited by the AI which presently lacks the ability to develop a strategy
in-situ so to speak, i.e. if the AI is suddenly given a colony of basically random development level and ships/ground forces of variable composition, it cannot readily fit these into one of the predefined AI strategy templates and thus cannot use its resources with any effectiveness. Given that the AI when able to follow a preset strategy is...not exactly robust, let's say...I can see why this would be a rather imposing challenge.