Thanks for taking the time to post here. The Mission Engineering pedals were designed for the H9 hardware, which only has 1 aux input. The H90 has 2 aux inputs, and can be used with a Y-cable to get both aux and expression pedal functions from the Mission Engineering pedal if desired.
There are many alternative aux switch / expression pedal or MIDI controller combinations that will work great with the H90. Using a an expression pedal that was designed for a different product may not be your best option.
The H90 has 3 on board footswitches that can be used for a variety of functions in Perform Mode. Using Perform Mode with an expression pedal with cover a lot of use cases.
Finally, our new Algorithm, PolyFlex, has an auto-engage function, which bypasses the effect when the exp pedal is in the heel position. So you don’t even need an aux switch for your RATM example, you can just use the PolyFlex example with a single expression pedal and it will bypass automatically. https://cdn.eventideaudio.com/manuals/h90/1.8.6/content/algorithms/pitch.html#polyflex
Let me know if you have any other questions.
