I prefer Male Blyeth too. Female Blyeth looks dead inside and not in a good way/.
I feel that Blyeth has their own share of downsides towards inclusion that you are kinda glossing over.
While Byleth is the central character to TH, it is clear that Edelgard, Dmitri, and Claude all are going to be key characters. They fill the traditional lord archetypes for their houses respectively. Furthermore, it is clear there is a certain... favoritism Nintendo has for the Adressian empire. We know the most characters from there respectively, and Edelgard takes up way more time in trailers than Dmitri and Claude.
Furthrmore, Blyeth's design works against them. Blyeth's weapon and design do not add anything new to Smash, which is something that Sakurai looks for when designing a character. Seeing Edelgard with a more unique design and an axe is something that tbh I can see catching his eye.
Finally, a neutral choice is kinda dead tbh after

and

.
Also I can't wait for the inevitable war to divide the three houses apart completely and we have to all unite for friendship and stuff.