I understand from the official Q&A that nozzle replacement isn’t supported, but have any users who actually have the U1 in hand explored the possibility of doing it anyway?
I have some high-precision, durable MK8 nozzles, so if it’s feasible even with a bit of forcing or modding, I’d love to use them.
My opinion - we have to wait.
Bambu Lab has similar design of hotends but you can buy the hotends with repleaceable nozzles (example: https://www.aliexpress.com/item/1005009787691786.html). Anyway, MK8 nozzles can be too big for U1 printhead.
I’m only one beta tester. I, for one, have not and don’t plan to explore any significant hardware modifications though.
Mainly because I’m asked for feedback to get the U1 working as well as it can out of the box. It seems making significant changes like different nozzles would make that hard to evaluate clearly. Not to mention the possibility of me making a mistake and breaking it!
That said, I’m very sure as soon it’s released to the wild, we’re going to see all kinds of interesting… modifications. 
The community’s been enthusiastic with ideas.