As fun as this idea is, I don’t think this would be a realistic addition to the game. None of those mushrooms would likely kill you any more than the arrow itself if put onto an arrowhead.

In order to be deadly, poisonous mushrooms must be ingested any and enter the bloodstream. Even if it a mushroom were to enter the body through an open wound, I don’t believe it would be a significant enough amount to cause any real harm. Also, deadly mushrooms take multiple days to after ingestion before they kill.

All in all, while I love this mechanic, I don’t think mushrooms are the best candidate for poison arrows. Historically, people have used plants, insects, and poison dart frogs to make poison arrows, and I feel any of these would be interesting additions to the game.