First off, I agree with many others that it would be nice if they implemented a mechanism whereby Great Works could be bought/sold/traded through diplomacy or war - instead of simply by taking cities.
I do want to point out that right now, you can indirectly buy great works of arts. In BNW, AI's are much more willing to sell cities and don't seem to place much special emphasis if there are great works inside. So if you find a non-capital city with great works (use espionage), you can try buying the city to get the great work. In a test game, Sweden offered me a 10-pop city with a Great Work of Writing for about 75 GPT, while Germany was willing to let a 11-pop city with a Great Work of Writing for around 150 GPT.
However, it would be nice if there was a formal mechanism that made it easier to do it. And so you weren't stuck with a stupid city too if all you wanted was the great work!
I do want to point out that right now, you can indirectly buy great works of arts. In BNW, AI's are much more willing to sell cities and don't seem to place much special emphasis if there are great works inside. So if you find a non-capital city with great works (use espionage), you can try buying the city to get the great work. In a test game, Sweden offered me a 10-pop city with a Great Work of Writing for about 75 GPT, while Germany was willing to let a 11-pop city with a Great Work of Writing for around 150 GPT.
However, it would be nice if there was a formal mechanism that made it easier to do it. And so you weren't stuck with a stupid city too if all you wanted was the great work!