One problem would be having odd colors where another color would normally be. For example, control-k 52 is red. If we use a 64 color scheme over 16 through 89, old clients would see something unexpected.
To tackle this problem in the best possible manner, the 64 color scheme (4 shades of each RGB color) could have the palette offset so each shade of red, each shade of green, and each shade of green, falls on a number that has a color similar to the old scheme. This would keep oddities to a minimum.
So if 20, 36, 52, and 68 are all red currently, then those could get the following RGB colors: 100, 200, 300, and 400 (being shades of red, with no green or blue). This process could be repeated with all shades, and then combinations as close as possible.
