I am working on a 5-10 year design a house and desperately hope monoblock air to water heat pumps with r744 (co2) are mature in the US market then. There are some, but it is still niche.

I am not a big fan of running lineset with r-410a or r32 in a confined space, too much risk of someone accidentally puncturing it. I would love hydronic systems to be more popular in the US. Being able to run hot/cold water in pex is stupid easy in both new construction and cheap in labor/materials. no noise concerns like forced air and much better routing for MEP imo. combined with an ERV, you can build a very good, high effiency zoned system that is comfortable and flexible.

Will see!