I wanted to mention that as well as I'm already doing the same, but was too lazy to type that in the end
Still it's a bit of a shame to waste the effort put into the domain you are going to liquidate anyway. But on the otherside, I saw cities completely surounded by walls with palaces being liquidated.
Those were only examples. I currently have 4.5k acres of wood in my domain and its overall size is at around 8.5k acres. So I'll never need to buy any wood (except for the rare ones). My economy is rather boring, because I only have wood, clay and stones. Farming is also not a thing yet, because I'm sitting in northern Tetra. So I'm completely relying on the tax money from my other domains.
Some expansions ahead there is a iron deposit that will bring a few interesting features to my main domain, even though I already have iron industry going in my other domains. I'm focusing on being independent from other domains and building a nice city, rather than going full maximum efficiency, but I guess this is a question of playstyle and my way of having fun.
Can you elaborate on the luctrative or interesting industries? I have one domain where I wanted to focus on building high quality lutes as it got quite a few rare trees.
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Q1: I don't think that is possible. The lighthouse will only open the ability to create trade ships, which can be used to trade resources between continents.
Q2: Direct trade is sadly not possible, so you have to do it the way you mentioned. Or you create a buy offer at the highest price and then sell it to your other domain. There is also a "tutorial" somewhere in the forums of the game.