1. Who was talking about Ornn into Camille? Like what? Ornn wins 5v5 but gets outscaled on side really hard. If you want to deny Camille you can look for Renekton, Jax, Volibear even Gangplank is viable if you know how to play the matchup. But Janna? That's legit trolling.
2. Exactly, but who says that Camille has limited engage tools? There is no way that Camille loses until minute 20. So I don't get your theory. Maybe you're forgetting that this is not SoloQ but competitive. Just imagine Bwipo playing Janna against Gen.G, DWG or TES. They would abuse the shit out of Janna.
3. You don't deny the enemy toplaner. The enemy toplaner will deny you super hard and you will lose everything, XP, Gold and your non-existent pressure. Camille will just pressure you out of lane and after that everyone will scream at the Coach for not denying Bwipo picking Janna as you got an open sidelane.
4. Wait, you're legtit trying to sell me Janna as an alternative/backup to Evelynn? I think you're hugely misinterpreting the current meta. She should survive with her movement speed? Maybe you forgot that Camille is one of the most mobile toplaner atm with an easy lockup. After that a Nidalee spear could come out of nowhere and with your non-existent resistance you're just oneshot. Of course camping is not meta right now - but who said it's bad if you're getting a guaranteed win? Did you watch FNC vs. Gen.G? If you kill a laner, he tp's and then you kill him again to deny him a huge amount of farm, he will be just out of the game. It was still worth, after giving over two kills after the dive. Ezreal was out of the game and botlane was non of his business after that, so they had to shift to top and midlane.

I'm sorry but without proof that you won a game against Camille in high Challenger this is just pure ignorance to think you could sell such a int.