I'm not sure if the gearing is the same on your TS as it is with my 2003 WRX. I actualy like the gearing and often take the car from a traffic metering standstill from 1st to 3rd (65 MPH) and pop it into 5th. Actually, the car gets it's fastest 0-60 just using 1st through 2nd.
Still, even with the WRX turbo engine I have no problem following a loaded semi out of a red light. The car isn't going to go any faster than I want it to.
Regarding your idea of oversized profile tires affecting RPM, etc. Yes if you oversize the profile and have a tire with increased overall diameter then the tire is going to travel more ground with less RPM from the engine. You can do the same thing by selecting a higher gear though. It's not a good idea to lug the engine more than needed when it's asked to work under increased load, like accelleration or climbing a grade. That's why shorter gearing is considered easier on the engine's lower end under higher loads. The WRX actually gets worse MPG climbing stiff grades in 5th (overdrive) and lower RPM than in 4th with higher RPM because here an engine lugging at 3000+ RPM is more likely to open the wastegate and engage the turbo.
What is a realistic powerband? These are 4-cylinder cars, not 6 or 8-cylinder and generally run higher engine RPMs for a given speed.
If you want lower RPM and don't mind less performance, shift gears earlier and use the highest gear practical for a given speed. Trying to do the same thing with an oversized diameter tire may work but it also adds the big handling and MPG disadvantage of higher unsprung weight.
Generally, the lower the profile the harder the ride. You can counter this trend by selecting an easy riding tire. Generally, you get widest performance advantages to using larger wheels and lower profile tires if the wheel/tire combination is lighter or close to the same in weight as stock and offers the same or larger tread width. You probably won't notice any performance advantages in turns with a 10mm increase in width. You will notice a difference with 20mm. Are you going to feel any difference in the pedal between 195/60/15 and 205/60/16? If both wheel/tire combinations weigh the same, probably not. Your speedometer will read 2% too slow, though.