yes, this is as I said in the OP...
it not hard, the hardware is quite easy , but you still need to prep a case,
also I think what is often overlooked is the effort required in the programming it up...
sure, its fairly trivial to just route the midi thru, but if you want to allow on the fly customisation, with a little app or web interface, that takes time, and also you need to ensure you have persistent storage for presets.
so depends what you have time for really.
ive built some interfaces for both bela and axoloti, but sometimes I just want to have something that works, so I can get on with other projects, or even make some music
talking of diy, to show im not against
I've a little tip, for Europeans - if you want a nice little box for your projects, I quite like the koma field kit, which koma sometimes sell
https://koma-elektronik.com/?product=field-kit-box-b-stock
18 euro is not cheap, but its nicely finished, 7 euros shipping, so better if your order more than one or something else from koma..
(ive now got a few, some from this b-stock, but also a couple from the field kits which ive moved into the rack)