So, the "solution" for having a gradient go from yellow to a blue (via a gray region) is to have yellow go through green and then blue? Color me unimpressed.

I remember years ago using non-linear functions to avoid a similar problem in a different field. I bet the same solution would work here and wouldn't look so "wrong". You could pick some non-linear fun to interpolate between values. And you could interpolate different RGB channels at an offset. The reult would be less gray in the middle.