It’s cute, I think. if I heard it on someone around me (in the Us) I would probably assume they were Hispanic. A lot of my Hispanic friends call my sons and theirs, mi hijo-prounounced just like Mio, basically, as they talk so fast.( Means my son)
I can only think of one name for it to be a a nickname for, Milo, if you pronounce it Mee-low. I’ve heard Milo pronounced My-low and Mee-low, so if you said it with a long e, I could see Milo becoming a nickname from that.