Though it's still extremely unlikely, it isn't impossible. Nincada, for instance, can evolve into something with a lower base stat total than itself, but it's still deemed better in combat (at least against the AI) due to having a much superior Ability. Granted, it's up in the air whether or not Abilities are used in Hisui; if not, there's very little reason to evolve a theoretical Bug/Rock Scyther into Kleavor unless there's something REALLY good about it, like an amazing signature move.
Oh yeah its definitely not impossible for there to be a regional Variant of Scyther. This is more a suspicion I have that it wont based on the unusual stat aspect of Scyther and its evolved forms having the same stats . I suppose they could arrange the stats differently to make them have different battle styles but as you say there might be limited benefit to evolving maintaining the type unless there are abilities or the signature move is really good (maybe stone axe will be really good). As for Nincada that's a bit of an odd situation given that you get two Pokemon out of that evolution. I suppose a regional form of Scyther would be potentially useful for future Kanto and Johto games but for me I don't think that's a strong enough reason.