"It's funny because I don't see many threads asking if posters should call their little boys Amelia or Sophie (not matter what the OP says). But calling little girls boy's name is "edgy" or subversive."
I don't see a lot of boys wearing skirts yet (thankfully) women being allowed to wear trousers is seen as progressive and modern.
You don't see little boys with girl's names because women are seen as the weaker sex so those boys would be seen as weak. Whereas girls having boy's names is seen as an empowerment. Maybe it's not how it should be, but that's the reality of it.
If you think about the best interests of the child, a girl with a boy's name is less likely to be negatively impacted than a boy with a girl's name.
Anyway, I personally don't find it shocking, depending on the name, though I wouldn't do it - I might use a gender neutral name instead.
This said, OP, boy or girl, I think Alpha can be a difficult name to bear on a daily basis
What about other Alf- names, Alfrieda or Alfonsine, which could have Alfa as a nickname ?
Or other names with similar sounds such as Khalifa for instance ?
Raphaëlle can be called Raphie which sounds close to Alfie ? Obviously it's a bit of a stretch as a way of honouring someone, but throwing this one there as it sounds like you love the sound of the name more than the actual connection ?