It is indeed a great concept Dom! You might be interested to check out this 2015 video, showing a bunch of cool possibilities for quad-reedplate twin-comb harmonicas. The bendy version is at the end:
https://youtu.be/sJGBnZXRHWg?si=AgLbWN8xwTsPAMsa
I tend to think of these collectively as Double Chromatics, but perhaps a better generic term to cover the multitude of tuning options would be 'Twin Slide-Harmonicas'. Whatever you call them, they're tough to make! (That is, with the same pleasing response and tone as standard diatonic or chromatic harps). Several difficult issues have to be overcome:
There can be a problem with Helmholtz Resonance Coupling, because of the longer air chambers. This occurs when the resonant frequency of the combined oral tract and comb/mouthpiece chamber is lower than the pitch of the reed. Then the two fight each other, with the result that the pitch of high reeds can flatten dramatically. In extreme cases, they can even stop playing altogether!
HRC was a problem with the bulky harps I showed in the video. It can be solved with a much more compact design where the reeds are close to the mouth, and the slimmer comb of the Trochilus will help with that.
Another big problem is airtightness, because you need two sliders. However one does it (two front slides, one front slide plus reedplate sliders, or whatever), that's two sources of potential air loss. Slide tolerances have to be super close.
To mitigate air loss, the easiest setup is with two fully valved chromatics. The option you want, un-valved or half-valved for interactive reed bending, is considerably harder.
However, I showed proof of concept of that in the video - so don't be dissuaded! With your good engineering skills, hopefully you can come up with a super-airtight, compact assembly for a double chromatic type of harmonica that plays as well as a single Trochilus.
If so, that will be something impressive. Good luck!