Is there a way to trade Factions for Prophecies campaign?

How would I go about that if it is possible. Thanks!

No way to "trade", exchange, or borrow another chapter from someone else. Once an account key is used, it can not be used for someone else.
"Trading", or if you will, giving away your account for ingame or real money is against the EULA and you will face the result of your account or both accounts being banned.

If you already used the key and activated the account, it's not possible.. But if you have the key, you can trade it with someone that want factions and have an unused propechies key.. Might be hard to find tho, and watch out for scams.

So you have an account with only factions, or a factions key, and you want to play prophecies.

You need to find someone with a prophecies key, or prophecies account, either on ebay, in game, or at work, and trade them your factions account for it. If you do this, they can steal your account whenever they want, and there's really nothing you can do about it. Still, if you trust the person, it's possible.

Except that's against the EULA and both parties can get their accounts banned....

I know it is. As has been said elsewhere, we can all have our accounts banned tomorrow for no reason. As far as I know, people don't actually get banned for this, so that is not a good reason not to do it.