Man, I was literally in the exact same boat as you. There is a way!
I got the 8 Plus on Verizon, and my girlfriend waited and got the X. Messing with the X Friday night I had instant regret. So here is what I did:
1. I got extremely lucky Saturday morning. I saw on twitter that Apple stores had same day pickup for the X at that moment and sure enough mine did. I went to the store, and bought an X on the iPhone upgrade plan.
2. For my 8 plus, I was using the device payment plans on Verizon. I paid the rest of the phone off.
3. I put my 8 plus up for sale on swappa this morning, and sold it within an hour for $700.
So now I'm basically where I want to be, which is with the iPhone upgrade plan from Apple (apple care included!), and no more device payment plan to my carrier.