Even that I multiple times said that ultimately I like Utopia DLC and 1.5 patch, Stellaris still has a huge amount of flaws and issues. Some of them can't be quickly fixed and probably require full-scale dedicated patch+DLC (i.e. Warfare), but it doesn't mean that just by tweaking some numbers or by introducing small mechanics there is no way to make Stellaris better game.
I'm not talking about bug fixes or something like that below.
So list is following:
1. Population growth, migration, colonization
First of all, I need to make a statement that I clearly understand from gameplay perspective why population growth is handled in non-realistic way (low base pop = faster growth, bigger base pop = slower growth).
Nevertheless right now we have a situation that at some point in game colonization becomes very easy, a lot of colonies are being created simultaneously and this means that with enough food empire population suddenly starts increasing exponentially.
Fix: Reduce growth of all pops by -25% at least. Reduce migration attraction, I can't recommend, but probably something again -25%. Colony ships construction should reduce pop on original planet by -1, when ship is constructed. Species that have less than 4 pops on planet can't be used for colonization.
Newly founded colonies should have modifier 'Newly colonized' that gives -50% pop growth for at least 10 years or until there are 5+ pops on planet. That should represent that low amount of colonists actually can't breed very fast, you know...
Desired outcome: Reduces explosive pop growth of empire in mid-game, reduces abuse of diversity of species in empire to avoid breaking of habitability mechanic - increases value for robot pops, playing tall, terraforming.
2. Mitigation of wide empires further
High amount of colonies and/or habitats (that can be spammed a lot) should incur much more internal stability issues for empire. Corruption, inefficiency, separatism, etc.
Fix: Every colony in empire should give flat +0.5% to ethic divergence on all non-capital core worlds or +1% on all sector worlds. Capped at +30%. Reduce impact from armies to Unrest - first army should still give -10 to Unrest, each following should give diminishing bonus, i.e. second = -8, third = -6, forth = -4, etc.
Every colony in empire should also reduce effectiveness of faction suppression mechanic or make it cost more in influence per month.
Desired outcome: Big blob empires should struggle to maintain internal peace and stability. This is risk/reward scenario - going wide is always better than going tall in Stellaris, ok, but you should know that going tall is easier.
3. Fast fix to galactic warfare
We are doing quick fix, not a patch+DLC, so this is going to be temporary solution until whole system will be redone from scratch. What is happening now is that one battle of doomstacks decides either you lose or win entire war.
Fix: Every military station should cost x2 more minerals, have their possible firepower reduced by -50% but gain x10 hull points. Every ship, that is damaged to less than 20% hp should have a chance every day (base chance like 30%; +10% if losing side, -10% if winning side) of combat to retreat. Retreating ships break from fleet and are MIA for some time, after than they show up on your capital world.
Desired outcome: Military stations will prevent ultra-fast conquests as they will at least take more time to combat and destroy. Retreat mechanic will reduce decisiveness of one battle a little bit.
4. Reduce pace of tech advancement
Fix: Increase cost of all mid-game tech by +25% and all late-game tech by +50%.
Desired outcome: Right now tech progress is too fast in mid and especially late game.
Hopefully all these fixes will reduce snowballing effect (when empire's power grows exponentially) that happens during mid-game with majority of player's (and some AI) empires. I think that this would make a game more challenging, less fast and, again, hopefully even after 150 years there would be challenges to beat.
I'm not talking about bug fixes or something like that below.
So list is following:
1. Population growth, migration, colonization
First of all, I need to make a statement that I clearly understand from gameplay perspective why population growth is handled in non-realistic way (low base pop = faster growth, bigger base pop = slower growth).
Nevertheless right now we have a situation that at some point in game colonization becomes very easy, a lot of colonies are being created simultaneously and this means that with enough food empire population suddenly starts increasing exponentially.
Fix: Reduce growth of all pops by -25% at least. Reduce migration attraction, I can't recommend, but probably something again -25%. Colony ships construction should reduce pop on original planet by -1, when ship is constructed. Species that have less than 4 pops on planet can't be used for colonization.
Newly founded colonies should have modifier 'Newly colonized' that gives -50% pop growth for at least 10 years or until there are 5+ pops on planet. That should represent that low amount of colonists actually can't breed very fast, you know...
Desired outcome: Reduces explosive pop growth of empire in mid-game, reduces abuse of diversity of species in empire to avoid breaking of habitability mechanic - increases value for robot pops, playing tall, terraforming.
2. Mitigation of wide empires further
High amount of colonies and/or habitats (that can be spammed a lot) should incur much more internal stability issues for empire. Corruption, inefficiency, separatism, etc.
Fix: Every colony in empire should give flat +0.5% to ethic divergence on all non-capital core worlds or +1% on all sector worlds. Capped at +30%. Reduce impact from armies to Unrest - first army should still give -10 to Unrest, each following should give diminishing bonus, i.e. second = -8, third = -6, forth = -4, etc.
Every colony in empire should also reduce effectiveness of faction suppression mechanic or make it cost more in influence per month.
Desired outcome: Big blob empires should struggle to maintain internal peace and stability. This is risk/reward scenario - going wide is always better than going tall in Stellaris, ok, but you should know that going tall is easier.
3. Fast fix to galactic warfare
We are doing quick fix, not a patch+DLC, so this is going to be temporary solution until whole system will be redone from scratch. What is happening now is that one battle of doomstacks decides either you lose or win entire war.
Fix: Every military station should cost x2 more minerals, have their possible firepower reduced by -50% but gain x10 hull points. Every ship, that is damaged to less than 20% hp should have a chance every day (base chance like 30%; +10% if losing side, -10% if winning side) of combat to retreat. Retreating ships break from fleet and are MIA for some time, after than they show up on your capital world.
Desired outcome: Military stations will prevent ultra-fast conquests as they will at least take more time to combat and destroy. Retreat mechanic will reduce decisiveness of one battle a little bit.
4. Reduce pace of tech advancement
Fix: Increase cost of all mid-game tech by +25% and all late-game tech by +50%.
Desired outcome: Right now tech progress is too fast in mid and especially late game.
Hopefully all these fixes will reduce snowballing effect (when empire's power grows exponentially) that happens during mid-game with majority of player's (and some AI) empires. I think that this would make a game more challenging, less fast and, again, hopefully even after 150 years there would be challenges to beat.