I would have no problem with them changing Hector or Isaac's looks, or even just an original devil forgemaster not seen in the games. As I said before season 1 released this is an adaptation of the NES game, any details that point to or reference wider aspects of the series is very much appreciated.
Though if it is Olrox, I really hope they don't go with the mistranslation. That's the one that bugs me more than any in the series. And I would hope he would look more like the classic Orlok, but just like I said above, any references to the wider series is a plus.
And while it seems clear that the vampire killer is not as presented in Lament of Innocence, I hope they don't make up some other progenitor of the Belmont clan. Either leave it a mystery, or just name drop Leon.