Turning Stiles into a werewolf would be over-kill, besides, he needs to stay human.

If he doesn't stay human then who would help Scott with his problems that only a human can help with,for instance that powder stuff they put around the club on i think the last episode,if stiles was a werewolf then that plan wouldn't have worked.

He should become a werewolf, but it should be accidental. Like he was in the way and claws were put into his sides and they were deep enough to turn him. Then he realizes he is a werewolf but accidental

We need an ordnary guy! We already have hundreds of werewolfs in a show. xd