Yes, there are many options and I LOVE that about the Marl V and the Mark IV for that matter.
I use an old Rockman Midi Octopus. Used it on my Mark IV before I got the Mark V and just made the transfer when the Mark V arrived.
Now I can control switching, loop, EQ, Solo from my midi foot controller. It's awesome!
The RJM products mentioned above are excellent as well. I just have 2 midi Octopus units from back in the day and they still work perfectly.
Anyway, bottom line is it can be done and it's relatively easy to do.
Good luck and have fun!