But I've been thinking about this for a while now. My biggest complaint right now about my A4000D is the AGA chipset. It seems to just fly when in 64 or less color mode, but in 256 color mode, work bench crawls, has weird redraws, etc.
I am simply dying for the Natami to come out, but the question always comes up "well when / if it ever comes out, what will be the damage to my wallet?" I'm also wondering if it'd be easier to create a new, faster, better AGA upgrade somehow to allow for faster 256 (or more) work bench?
The FPGAARCADE is your only hope now that the Natami fire has fizzled out... but that is only going to support a GFX card mode, and not a superset of AGA.
Anyway, I agree that AGA was a little slow out of the gate - about 1/2 the speed of a mac of that era in 640x480 (multiscan) 8bpp mode. They were also less than 1/2 the price. Commodore probably expected most people to use a NTSC monitor like a 1084 anyway...
If you have an Indivision AGA MK2 you may see a driver in the future that does not slow down so much running in higher resolutions or depth. The driver would accomplish this by turning off screen DMA while writing to the video buffer. Normally this would cause the screen to blank out but the Indivision would frieze the image until DMA is reenabled. You could see a quicker ShapeShifter or WorkBench driver.
In higher resolutions and color depth the machine just spends way too much time being locked out of the chipram just displaying the screen. 256 color mode in theory should be 1/2 the speed of 16 color mode, but as you know, its much slower than that. Not only do you have twice as much memory to move, but you have to use a much smaller shovel.
Also screen changes would probably appear instantaneously and you would never actually see anything being drawn. That last part is just speculation on my part though.