At least you don't need crazy-expensive manufacturing processes. Assuming you actually mean improving the pen part and not just making pretty barrels (quite the cottage industry I understand, but I was always bemused that they all seem to sell their pens with the shittiest nibs because presumably the art/craft country-market is insensitive to that), have you looked into 3D printing? The nature of how the material builds up from molten threads naturally leaves a rough surface that I suspect would be good for capillary action in the feed, and I suspect that a capillary feed is the easiest low-tech one to get right - nothing more frustrating than a too-fast or too-slow pen.

I'm not sure if you're into flexible pens, but I'd be very interested to see a calligraphers' flexible nib (one that spreads under pressure for varying line width) that is NOT subject to damage from going that little bit too far, e.g. through a sprung hinge instead of flexible metal. Adjustable spring preload for fancy-pants points.