I'm not sure who that call to action is addressed to. ARGB texture support for SDL2 was already added to TinyGL, it's verified to be working, and it will be available in MorphOS 3.14. If someone in the meantime wants to write a new SDL2 renderer from scratch be my guest, but I'm not even sure what API would they be using for it. If you think CGFX, you'll quickly discover that most of the work still has to be done in software. The video subsystem in SDL2 is very different from SDL 1.2.

edit: I take back my comment about MOS 3.14, apparently the TinyGL update was not included in this release. Again, this is not something me or BeWorld has any influence over.