OK, first of all I still cannot understand why you are trying to invent the wheel. Plenty of kits are already for sale, and some are pretty cheap. Anyways..... I am only saying this because I have already done what you are doing now. Difference is, I have my own machine shop, I am an engineer, and I know that I had to go through 4 versions before I got it right. Why did I do it? Because I had the know how and the resources. If I did not have my own shop, I NEVER would have tried to design and develop my own design. The economics are not there. But by all means... go ahead and try.
I can tell you this, there is a reason why the stock lever has an angle design in. Your design uses a straight single rod, with no angle. You will find that the lever position is virtually unusable for most human beings, not to mention uncomfortable, when there is no angle designed into it. How do I know? Because that how I did mine, at first.
If you want, I would be willing to share with you my working prototypes. And BTW, the distance from the pivot point to the ball/socket center is very specific, and defines the whole short shift motion. Too long, and you cannot get it into the socket because of the linkage interfering. Too short, and you don't get much difference from the stock shifter. I can tell you this because, well, I have prototypes and the first one didn't work because it was too long. Let me know.