It's all about who he faces in his debut. If you're running vignettes and his first match is against a face then obviously, he'll be the heel. If he's facing a heel then he's a face.
And I'm not talking about jobber faces like Hurricane, Stevie, Tajiri etc. because when he debuted, face Val Venis defeated face Scorpio and in his debut, heel Chris Masters destroyed heel Stevie Richards. Make his debuted against a midcard heel if you want to portray someone as a face after running vignettes.