On second question, I think this not under the control of Arcane Studio anymore. GOG could add whatever binary they want to the rest of the game, e.g. also the ArxLibertatis version. (But asking the ArxLibertatis project would be a nice move of GOG, even when not required by license.)
I'd imagine the distribution/licensing agreement GOG.com has with Arkane/ZeniMax limits what changes they aee allowed to add - any problems introduced by them would reflect badly back on Arkane. *I* certainly wouldn't have a problem with including AL though (and the source code license allows that anyway).
Using this version has actually made the framerate worse, in addition to a whole lot of graphical bugs, textures moving around on objects.
First, try updating your graphics drivers (and for NVIDIA Optimus, making sure it runs on the right card) doesn't help. AL 1.1 uses OpenGL instead of Direct3D by default and unfortunately for some HW/drivers that unfortunately seems to make things worse. Also, our OpenGL renderer is not as optimized as it could be - now that D3D support has been removed in the development code, it should be easier to restructure things to work better with GL. We hope to have performance improvements in AL 1.2. For now, you can try switching back to the D3D renderer with AL 1.1.x in the video settings - be sure to restart the game for it to take effect.
As for the graphical bugs, care to provide more details and screenshots?