Thanks everyone for the help so far! I had liked the idea of the Euro plug mainly because I could then easily use small antique home machines from Italy without the need for rewiring anything. And it would let me skip rewiring the plug, and keep more of the machine in original condition. But given the code issues, I suppose I can just source a plug converter for use with vintage home levers.
I'm not worried about the hertz, as there is nothing more complex in this machine than an auto-fill circuit and a pressurestat. They had asked what power I wanted and I told them 50 hertz just by looking up specs, but reading more it sounds like that would be very hard to arrange and would not produce any real benefit.
Dave, if I am reading right, your solution would involve there being no plug at all, just a hardwired connection from the machine to the wall? My only concern is that this might complicate uninstalling the machine if I want to replace it with something else down the road. I'm not anxious to do so any time soon, as I'm excited to see what this one can do, but given my history with coffee gear I have to admit that buying something else is pretty likely over the next ten years.
And does everyone agree that if I do go with a plug and receptacle, a NEMA 6-20 is the way to go? We have 20 amps to this outlet, mainly to ensure it will be rated for the future if I ever upgrade to a 2-group commercial machine.