Well I thought the use of "O" and "I" were much as you say ff. There is something quite aggressive and disruptive (even masculine) about "I" where as "O" is appears much more feminine. So I think those letters were chosen very deliberately for each woman. More interesting is "U" I think - what do you make of the disconnected circle? That she is somehow unhinged? She seemed a bit unbalanced to me.
Going back to vowels vs consonants, I guess we need to take this in the context of the Russian alphabet rather than the English alphabet. In Cyrillic we actually have 11 vowels and 20 consonants but 33 characters because of the existence of two pronunciation signs. I don't know enough about this alphabet to say anything terribly educated about it, but I guess we should consider this when talking about the whole vowel/consonant thing.
What I was mentioning earlier was based on pronunciation. Vowels are usually open sounds whereas consonants usually involve the clipped sounds of the mouth or tongue creating a closure. Oh - if only I remembered my brief linguistic training I could say that much more precisely but hopefully my meaning is clear. It could be the consonant sound might somewhat approximate the phallic or penetrative nature of man whereas the open vowel sound might approximate the open or penetrated aspect of woman.