Hi and thanks!
I am really overwhelmed by your positive reactions. And I really like your suggestions for an advanced design - especially the attachment point for a hand strap. And probably it is possible to integrate an Arca Plate into it - but that would be a little more complicated. Plus I rarely use a tripod
I am not too afraid of Chinese knock-offs - if I encouraged anyone to produce accessories for Pentax, that would be a nice thing. I don't think it is sophisticated enough to be patented
I was actually inspired by some smaller micro4/3s-cameras, where aftermarket add-on grips are already available (and more needed, I guess) like Olympus' OM-D series.
And unfortunately the grip is not compatible with the K-5 at the moment. It attaches just like the original battery grip by the tripod mount and a pin next to the battery door. That pin is in another position on the K-3 than it is on the K-5, that's also why their battery grips are not interchangeable.