Oh man, you beat me to it! I was thinking of trying this just the other day. Great to see it works.
Watching this, here’s the exact thought process I went through:
Uh, OK, another electronic toy. A MIDI melodica, I guess, with an uilleann patch. Fine. Seems to work. Doesn’t sound much like pipes, though. Hmm, I didn’t know Hohner makes a MIDI melodica. Where’s the cable? Wait … why is he wearing a bag and bellows? Why is he … Oh. Ohhhhh. I’m an idiot.
I had the same idea a few years back. Took it to the Muddy Rudder pub, piper Preston Howard was there, and he had came up with the exact same idea at the exact same time. Kinda trippy. Preston just connected everything up with duct tape; I turned out a wood plug to fit into the melodica, and made a brass fitting to go into the chanter stock out of tubes soldered together.
The idea was to have something to play fiddle tunes on; I used to just play the fiddle for that. Gave up on the melodica as you needed a table to put the thing on, and would have to be unplugging the chanter all the time; also you’d face the usual piano accordion haphazards, i.e., hitting the wrong note by mistake, or “playing inbetween the cracks” as it’s termed. These days for a second instrument I play the banjo-mandolin, which is just what it sounds like. With only 4 strings it’s much easier on the ears.
“Uillodical Mr McCoy”
There’s nothing like thinking your ahead of the crowd, only to find your really at the back of the line!!
Must be something in the water up here that makes a man want to strap a melodica on the end of his bag.
I bought a “Mylodica” brand melodica, those have a wood case and brass reeds. Then I bought a used full size Hohner 37 - the Mylodica is smaller - and made a Y adapter, to be able to play both at the same time… 
Never drank enough to get around to test driving that one, actually. Or forgot about it? Would make for a nice way for a Hammond organ player to busk, I guess. Or you could just learn how to play the accordion.
The Mylodicas are built by hand, I wrote the guy who builds them about my invention - never heard back, guess he doesn’t care. Incidentally you hold these with the left hand through a strap on the bottom, and play the keys with the right hand - I yanked the straps off mine so they lie flat on the table. The bellows are an obvious way to avoid getting the reeds damp, obviously. My piano playing father used to pick up the melodica as a change of pace when playing in clubs, his old Hohners are all full of white crud… 
Would be nice to tape down a few keys for drones.
Tried this idea a while back using a 32 key Excaliber (airtight) for the melody melodica hooked into the neck of the bag and a Hohner red alto melodica ( button keys) for the drone or drones out of the stock cup. A non drying clay putty from the hardware store was used in the tube inside the mouthpiece of the Hohner melodica to reduce the rate of airflow and the sound volume as well. Without it the melodica took way too much air. Rubber bands were used to depress the desired keys. Worked fine and sounded nice.
One can also use the Hohner melodica as a drone system hooked into the neck of the bag. The melody melodica is played as normal against the drone. Also makes for a drone system for whistles. The low F below middle C on the melodica as a drone for a low F whistle.
This post reply might be a replay of one I tried sending earlier that didn’t seem to go through. My first attempt here, hopefully this one registers.