I think you're being imprecise when you say interrupt engine power; it's also there to modulate engine power. You can ride 5th gear at sustained 10 mph, provided that you stick the clutch deep into the friction zone, but from what you've told me it's counterproductive.
I was just asking whether or not you could get the effects of sprocket changes / gear ratio mods to some extent by using the clutch to force RPM into higher torque territories. You told me no, because the clutch in the friction zone eats up any increased torque, and I accept that.
Ironically, if you drive cager vehicles, educated hypermiling is often more fun than naive granny-driving, because granny-drivers want to drive 1000-1500 RPM, while hypermilers want to do half peak torque, which is often between 2000-2500 RPM. The RPM control does reduce your acceleration compared to driving at peak torque for max acceleration, but you get a good combination of fuel economy and performance. Amusingly, when I introduced Mom to using half peak torque to increase fuel economy, I ended up having to remark "you're an old lady, why can't you drive like one?" because she was driving so aggressively.
With a motorcycle, unfortunately, most bikes are ridden above half peak torque, so while acceleration is more brisk and more fun, fuel efficiency is lower. Practically applying RPM control to motorcycles seems to be more a matter of aggressive upshifts, i.e, the CBR250 hits peak BSFC at 3700 RPM, so the two challenges there are to upshift as soon as the engine can support it (BSFC maps usually suggest that more throttle / higher gearing increases fuel efficiency faster than moving towards half peak torque), and to stay around 3700 RPM once you hit an optimal engine gearing.