Jady stick at it. Looks like u deffinatly no what u doing. Pick a few parts that we cannot get. An item that actually peoe need cause there machine doesn't work means they will pay at a higher price.
Plus I bet you actually enjoy designing these parts other wise you wouldn't spend so much time on it. Maybe take a break for month or two. Get u head in a good space. I'm sure you will come up with even more great ideas.
Even flog it on a cheap website and plaster them across all the forums. I'm sure there is guys on here that could make a cheap website for u. All the best mate. People like u are what this hobbie needs.