Not sure what goes on in the brz but here's what subaru does on the sti.
http://www.iwsti.com/forums/diy-mods...-method-4.html
They add the delay valve to prevent you from shocking the drive train by sidestepping the clutch or just releasing it quickly. The clutch itself is also sprung too for this same reason. Removing the valve from the slave cylinder is more likely to make your shifts jerky than anything else.