When I first read Mya, I pronounced it the way you intended - I don't think you'd have any pronunciation issues there. I prefer Mya to Milla; have you considered Myla? My wedding photographer named her daughter Myla (My-lah) and it could be a creative way of combining the two names you like... the only reason it's not on my list is because my #1 girls name is Skyler, and I don't want rhyming children!

I also adore Ruby although it is becoming super common these days (I work in Births Deaths and Marriages ). You can't go too far wrong with pronouncing Ruby, so maybe you could play around with variations? Favourite one I've seen so far is Rubii which I thought was very unique and would have stolen for my names list had it not been suggested by 6-month-pregnant BFF. Ah well