Yes, I'm "unable" to receive payment as in "legally unable". Taxes and labour laws can complicate things, certainly outside the USA.
As for the feature list, thank you for detailing it. You can make a new page in the Wiki with your feature requests and link the Roadmap to it.
Now for the features already on the list:
I'm interested myself in texture compression, but I'm unsure how the API should look like, and also, we need to use compression code that is zlib license compatible.
Optimizations are always welcome, as long as they don't threaten the stability of allegro.
Bugs should be fixed, and I hope someone who has OSX will see into why al_create_bitmap doesn't fail correctly.
Monochrome bitmaps could be interesting for masking effects or simple shadows. I'm also somewhat interested in this.
In Allegro, bitmaps should be loaded after setting the display mode. There's not much that can be done about that, and IIRC, SDL2 has the same limitation...
Which changes does the sound system need? Is it currently not accurate enough to play perfectly matching "tiled" sounds? What are "Tiled" sounds anyway?
Simple 3d rendering is already possible in 5.1 with perspective transformations and al_draw_prim, etc. There was a thread in the "programming" forum that had examples on how to do this.
Multi threaded rendering is likely to be impossible since that is a limitation imposed by the Windows API. The rendering thread must be the one that opened the display window. SDL2 also has the same limitation for the same reasons.
I'm not quite clear what you mean with "post-draw" antialiasing. Could you describe the problem more in detail, as well as what kind of effect you'd like to achieve?