OS4 is not done, AmigaOnes are not available and there is a good chance they won't be available again, so I think AmigaOne with its hardware flaws is a bad idea. Troika is supposed to be coming, it gets away from MAI's flawed part, so it should run better then the AmigaOnes, however the OS is still not done, why buy a computer to run an incomplete unfinished OS thats 3 years late at the moment.
But according to those who have aones, the OS4 prerelease is fully usable even now, even though it misses some features of the planned final version. If he is ok with how the pre release now runs, then why should he not want it?