That’s a fantastic idea. There is actually a thread in this forum called “Tool Talk” that I think would be a good fit for this. You might consider starting a thread with your home made tools. BTW, a belt tensioner for the K series is an awesome idea. It is difficult to get in there and you do need to apply quite a bit of leverage on the tensioner to replace a belt.
I did cover some of the tools I used on Hondas, some of which are home made, and also some of my other tools in these videos.
It might be time to revisit the topic with ‘home made’ tools.
Thank you for the suggestion and good luck with your future projects.