Figueroa Brothers, Inc. of Dallas, TX has an answer to all these odd-ball soda-flavor combinations coming out these days: sell bottles of flavoring.
Soda Splash is a pressurized can of flavoring that you can spray (or spritz) into a glass of soda, allowing you to create flavor combinations.
They come in three flavors, Cherry, Lime, and Vanilla.
So, you can create a Cherry Lime Rickey by shooting in some Cherry and Lime into a glass of 7-Up. Or, you can make your own Cherry Vanilla Dr Pepper. Or how about a Lime Vanilla Rootbeer?
The company says it contains no sweetener, and adds no calories.
I don't know where or when Soda Splash is available, but you can keep track of it on its own website...