Hello,
Thanks for your post!
Yes, the MIDI IN port could be used for connecting third party MIDI gear.
There are also two 'EXT' inputs on the iRig Stomp I/O. These can be used with expression pedals or foot switches designed for MIDI controllers.
If you are using iOS or macOS, check out the iRig BlueBoard. I use these devices together all of the time. They are great for sending any MIDI CC or MIDI PC messages needed.
https://www.ikmultimedia.com/irigblueboard/