I think [name_f]Frankie[/name_f], [name_m]Max[/name_m], and [name_m]Kit[/name_m] are already halfway there. [name_f]Frankie[/name_f] and [name_f]Stevie[/name_f] seem particularly well matched to me.
I could see [name_m]Alfie[/name_m] and [name_m]Davy[/name_m] crossing over, though I think they have the disadvantage of not having a popular feminine full name like [name_f]Frankie[/name_f] “Frances”, [name_m]Max[/name_m] “Maxine”, or [name_m]Kit[/name_m] “Christina”. [name_m]Even[/name_m] when the name is used as a full name, I feel like there’s more chance a nickname will cross over when there is a feminine full name in mind.
Nicknames I’d like to see cross over more widely: [name_m]Otto[/name_m], [name_m]Teddy[/name_m], [name_m]Louie[/name_m], and [name_f]Georgie[/name_f].