I like it as
Idonea best, then
Idony, and I don't care for
Idunn. (looks like "I dunno" typo-ed.)
I'd go with a traditional plain or traditional unusual but not off-the-wall middle name. Or I would use it for a mn with one of those types of first names. I don't think it's too out there to use, but I don't know that I would use it. Hm.