Much as I miss building hurdy gurdies, using my current one for 1.5 years now is teaching me a huge amount about what to better next time. Dragging it around Europe in a rucksack was an excellent stress test, and the various repairs I’ve had to do (and continue to have to do) over the last few months highlights areas I need to put more thought into in the future.
For example, the aluminium axle with setscrew arrangement is inadequate due to it coming loose over a period of 6 months, the trompette disengager I made was much too fragile, the strap knobs need to be glued into a solid, well-attached internal block making contact to two planes, ditto for the bridge-end string holders — having them pull up against binding (which the instrument would be better off without anyway) is inadequate. Additionally, an adjustable melody string bridge is a no-brainer, and building custom capos is almost certainly unnecessary and produces worse results than just using harp capos.
Edit: having said all of that, it’s still a good-sounding, stable, very playable instrument.