Again, these suggestions sound like "render two alternating and differently calculated 16-bit images instead of fully 32 bit images". The industry is just going to have to accept the performance penalty if 3D manages to gather enough momentum, just as it accepted 3D acceleration, 32 bit color, and so on. KZ3 might not look that good in 3D, but by the time we get to KZ4 people may not care about the 2D resolution at all.
Only in this instance the analogy falls down as we don't have the equivalent to that 32 bit hardware. All the industry has to work with are Vodoos and there are no 32 bit graphics cards available (no new consoles with better hardware). Developers don't have to accept performance penalties because they could just as easily ignore the technology for the coming 2-3 years without penalty.