I'm not sure this would work great.
Making a string non-homogenous in construction would be disastrous, IMHO.
The vibrations and wave patterns would become non-linear and give unexpected results.
Maybe that would be interesting though!

At least the differences should be kept at a minimum to provide better bowability, if that's what you're seeking.
Sanding the bowed area doesn't help?
Using nylon hair (like those cheap Glasser bows) either?