I think you mean Nov. 2011, MY2012.
My car is a late MY'12 build, I think it was built in May 2012, and it has the screw on knob. I ordered the car right before the cutoff date for '12 MY orders. Based on that I would think this change was maybe implemented for '13 MY builds (unless someone has shown otherwise?). That, or they contracted the part out to a new supplier and they implemented over time, with several functional build trials before 100% implementation.
XR, maybe you'll need two different threads inside the knobs depending on which type of shifter. For earlier builds with the threaded knob you already have a design that works, but for later builds with the press-on knob maybe a larger thread diameter is necessary, one where the minor thread diameter just clears the knurling on the shaft so that the owner can epoxy it in place. Another thing to try might be LocTite thread lock, and to remove the knob you just need to heat it up before twisting it off.
With a little creativity (and since the knob is billet aluminum) you may get away with one thread for both applications just boring the knob to a slightly larger diameter than the "ideal" spec for the thread, and then threading it. The thread's pitch diameter and major diameter would be the same but the minor diameter would increase. I don't know if this would work or not, you'd have to measure the diameter of the press-fit shaft knurling and then look up the diameter specs for the (M10x1.25?) thread.
Another thing to consider is whether the thread inside the threaded knobs is tapered or straight. I have a feeling it's tapered and this is how the knob gets tight as you screw it on. Mounting a billet aluminum knob with a straight cut thread may require the use of LocTite to secure it in its final orientation if there is to be engraving on it and you can't bottom it out to tighten it.
It may be neccesary to index the threads relative to any engraving done to ensure the knob sits properly on the shaft relative to the reverse lockout collar (not an issue without engraving). I know if I tighten mine down an extra turn so it's really tight the knob sits too low and the collar won't lift enough to get it into reverse. I would imagine the threads on the shifter are indexed for this reason but you would have to look at several cars and compare where the threads start to be sure, they may not be depending on the mfg process.
Anodizing is a great idea as it will toughen the surface and make it more wear resistant. A project I worked on a while ago had some prototype parts "hard" anodized and the resulting finish was kinda cool, a matte grey kind-of and apparently very durable from a wear standpoint. Be careful specifying funcional or Engineering processes for a cosmetic application, though, as often the process will vary with little attention paid to cosmetics.
Anodizing can be very wear resistant, but it is a very thin coating and will not resist deep scratches or denting much more than the base material. Choosing a base material with higher hardness and scratch resistance will make a more durable product, with or without anodizing. Soma aluminums take to anodizing better than others, your shop connections would be able to advise you on this with advice from their anodizing place.
Just tossing some random thoughts your way. Cool project, sorry I didn't see the thread sooner...
