This seems like a good idea, perhaps colonialism as a technology to build cities across oceans might be a good gameplay implemention of colonialism, without the more problematic moral and ethical issues such a element entails.

I love this idea.

I think having the ability to have colonies, vassals, junior alliance members etc... all cool mechanics that make a game more interesting and more realistic.

I also think by having a colonialism system that only lasts for a certain period, you are encouraging something like what we saw in real human development. If you are a successful ruler, you can turn your colonies into a supportive Commonwealth like the British did... and if you are a bad colonial ruler, you will see all of your holdings violently revolt.

This could be a setting in the difficulty selector, as I imagine some folks would prefer a more "CIV" style of play where you own what you conquer. I think Amplitude is already kind of going in the right direction if you look at ES2 and influence and how that mechanic is quite similar in concept to what you are proposing.

Upvoted!

As far as I can see Portuguese or even Iberian cultures are not present which severely damages the idea of colonialism as a culture choice. Miscigenation was always a thing as Portugal was very small. On another side of the spectrum, and much later, we would have the English with a strategy much closer to your idea. I believe that by missing some of the capital cultures the game will be limiting the notion of colonialism to the 19th and 20th centuries.

We could have a sort of apoikia colonies by having the greek and phoenecian cultures with a much more independent colonization which might not be exactly what is intended for this sort of game.

Cheers