I had been drifting towards Celtic MNs for
Oona, partly because it's an Irish name itself and partly because it avoids that "one" thing (which is also part of why I don't like the spelling
Una). Things like
Oona Ceridwen,
Oona Myfanwy, and
Oona Meraud had come to mind. I do like some of the Germanic ones, but they seem to take
Oona to a harsher level. Some of the Greek ones you have make me smile, though... especially
Oona Calanthe. That looks lovely. :) I also like
Oona Bryony,
Oona Mairead, and, oddly,
Oona Hyacinth. I usually don't like
Hyacinth at all.