Thats a pretty good one. Its simple and a classic teamup with guest star hero against guest star villain but sounds a lot of fun. Though personally I would be upset if we would get anyone from the Batfamily (in ther hero identities) before we actually get Batman.
What would the first meeting between Oliver and Dick be like? (Discovering that there are other vigilantes outside of Starling would be a pretty huge thing on the show at this point)
Does Shiva have ties to the League of Assassins? And if so do Sara and Shiva know each other?
What would you call your episode?
But yeah Shiva is an excellent choice for a villain on Arrow. Fun trivia: Shiva was voiced on Batman: Arkham Origins by Kelly Hu who played China White on Arrow (and Deathstryke in X-Men 2)
we still need your story and details. just dropping two names doesnt make an episode :P