Randomizing by polygon islands

[SSmolak]

Hello,

Is there other way to randomizing surface properties using nodes by disconnected polygon island than using fracture like this :

Problem with this method is that there is hard to make them real random and fracturing is very slow in complex object. Only two nodes works with Fracture and random effector : Color Shade and Instance Range connected to gradient.

Is there any Instance ID workaround to polygon islands ?

I dont' want to make them as instances - it will be used for extruded polygons like bricks, wood planks etc.