can we do a double brush system (2 or 3 brushes together) for example "when we draw a line or curved line can we add a totally different brush like we draw the trunk of a plant and the random leaf brush added to it. With such huge brush system and scripting ability may be we can implement it.
The old vector drawing program Livebrush (https://www.facebook.com/Livebrush/) have it.
Another suggestion is node based brush system. Something like Blackink(http://www.bleank.com/BlackInk-a115.html)
Sorry for my mistakes. English is not my native language.
I asked same quistion in krita form also. But answer was no.

Not sure whether I did understand properly your request, but Gimp has brushes type .gih to produce different output stroke after stroke.
This has been done using vine.gih brush.

see also
https://www.gimp.org/tutorials/Image_Pipes2/

They are single brush with animated layers. What i am looking for is combination of 2 brushes at same time.
Something like a base brush + a decorative brush.

2 different brushes with adjustable spacing.