I haven't emailed before about this - a standard 'seconds of downtime' move would almost always be fine - but before you started this thread, I had been wondering if you were thinking of having an ARM64-based server now these are looking interesting. 

It would make transfering VMs directly rather harder (you'd want native ARM64 binaries, rather than relying on emulation of existing x64 ones) but the number of cores they come with and (presumably) the lower power requirements could make up for that for fresh VMs. 

(It also reminds me to be sad about your other recent post about Debian dropping i386 - I still have a couple of netbooks that won't do x64.)

Ian