But using a clutch with a manual gearbox is interrupting power flow from the engine to the wheels. If you have powershift, use it!
How often do you press the clutch when you're not changing gear? So why press a clutch when you are changing? Surely better just to have uninterrupted power from engine to wheels. There are single clutch "dual clutch" transmissions (if that makes sense to you) in design, for people that want to interrupt the power during gearshifts and operate a clutch themselves, but they are people that are resistant to change; they will be slower since the engine is effectively off for the duration of the gearshift.