I just have to point out the fact that 90% of the time it took for 2.5 to be finished was getting the new code to work with the old code, not because adding new features is hard or takes 9 years. There was so many bugs at one time that the ZC bug forums were split into many subforums.
Also, I did take a look at "TilePattern" and co. It looks like animations have to be exactly 4 frames and there is a static frame counter in there as well, meaning all animations are the same duration even though a TilePattern is virtual (More red flags.. This actually doesn't even make sense). I was also pondering, it seems, about how a "Tileset" was a Bitmap with extra tile information. I was also correct about how there is no true low level data design in the rendering pipeline: Everything is object-oriented and treated as though only one ever exists, then shipped to SDL. (Unless I just happened to miss a file or two) :/
If you talk with him maybe just ask him about that.