Alpha Centauri had really great naval warfare:
1) Naval cities could be directly attacked/defended by ships
2) Ships could bombard offshore hexes destroying any terrain enchantments like farm or borehole which took quite some time to build
3) Ships could bombard ground units damaging the whole stack
4) Ground forces could use artillery to have an artillery duel which lasted until either the ship or the artillery died
5) You could raise water levels in UN charter meaning now more cities could be attacked by ships and even some cities could sink if they didn't have naval city improvement
6) Assault ground units could attack offshore cities directly from transport ship which was a very dangerous threat because typically you didn't see the transports until they captured your city
Alpha Centauri had really great naval warfare, if you think that Waterworld should be the name of every movie. The naval units in that game were so grossly overpowered that it was stupid. I purposely beefed up my fleets in early game, got the 6/6 and 9/9 upgrades, and dominated the entire world with my horrifically OP Tier 3 naval units that could not be killed. I regularly conquered entire planets starting with like 10 or 12 naval units.
Civilization VI now does that a bit better, as they don't 1-shot everything, and have good usefulness without being utterly OP. Still crazy powerful, but not as bad. That approach is impossible to use with this combat style, with multiple stacks in combat through completion, but there may be some middle ground.
As for the Original Post:
■ what i would keep from planetfall:
and
■ what i would keep from AOW3:
For this, I think that there is a 500 lb. gorilla in the room. Without a better AI, there is really just no hope. This is the absolute bane of these games, but it is something that simply cannot be overlooked.
As of 15 days ago (my last game), there was no losing. The computer's city management was abysmal. The computer's combat strategy was singular and abusable. Unless it was 4:1 or worse, the computer was about to get smoked, maybe even without losses. The computer would just expand brainlessly, and even with perfect visibility, (it sees the entire map and knows where all of your assets are), would regularly overextend and get itself overwhelmed.
The AI is just so bad that almost no matter how much you let it cheat, that there is just no real challenge. Sinsling did a 12 v 1 insane AI, hardest possible settings, stupidest possible playstyle, and it was close. I regularly did 12 v 1 just for the heck of it, and never even bother to save. Empire mode made it better, but that is just because it cheats even worse now.
I fear that if you want to make a more compelling game, you have to have more compelling opponents. The AI just isn't doing it, and that is too bad. There is only a few ways change this though, make a smarter AI through lots of hard work, or use machine learning to shortcut it. I have never done either, so good luck to them on this, I wish I could help.
And as for the gameplay itself, that is beset by another 500 lb. gorilla. The UI and city management tools are unfinished and unhelpful. So much so that conquered cities feel impossibly hard to manage. I have posted endlessly on this, so I will save it here:
There are two types of problems with Empire Mode...
And this feels a bit like the previous issue: in that it would benefit from lots of polish. It is different in that it is really mechanical, so it feels solvable, if Flagship put in the work. But they never have, so who knows if it will ever get solved. I just hope that when the next AOW comes out, the interface doesn't suck for no good reason.
This all gets me to what they did do right. This Empire system is incredible. This is a modding system which is fully integrated into the game. I don't believe I have ever seen anything like that before, and they are really onto something. If they can get that right, maybe this is the breakthrough that changes everything. It is limited in that they
really lean into cheating harder than ever, but it works anyway. I have had more close calls with this system than ever. And think of what else they could do. I mean, try the original quests using an Empire-mode system. That would be pretty damn sweet.
So whatever they do, have Empire mode be a part of it. And use all of the good ideas from your modding community. It could really be amaing.