Illustrator extension for brushes

Hi all, I'm making brushes in Illustrator, and just feel that it's not quite enough options to play with, to achieve a result that I need.
And think to make some sort of plugin \ extension for brushes.
The question: is it possible to be done graph interpolation function to parameters like "Spacing" or "Size" as it can be done by pen on the tablet to achieve the result with thickness \ gaps variable value.
To make possible to use for texturing without a pen tablet.