Just remove the needle from the gauge?
Mine goes to 11
Not always.
With much older automatic transmissions, there was always a certain amount of “slip” in the torque converter. The amount of that “slip” would vary with the amount of force going into the transmission relative to how much resistance the vehicle is encountering against its attempts to remain in motion. In a given gear, at a given speed, you could expect that your engine would be revving higher going uphill than downhill.
This “slip” is why historically, automatic transmissions used to get poorer fuel economy than manual transmissions.
I don’t know when the “lockup torque converter” came out, but I am sure that it is standard on all modern automatic transmissions. Most of the time, the torque converter is locked up solidly, with no “slip”, but the lockup does briefly disengage under certain circumstances to allow smoother standing starts and shifting; and when it disengages, engine RPMs would go a bit higher than they would be in the same gear at the same speed with the lockup engaged.
This is indeed a very good point. Even if the vehicle otherwise seems to be running reasonably well, there could be some underlying issues resulting from the ECU receiving bad data on the engine speed. It would be a very good idea to get access to an OBD-II device that can report the engine speed as seen by the ECU. If the OP has an Android-based smartphone or tablet, then I would suggest spending about $20 or so on a Bluetooth OBD-II adapter, and I think it’s about $5 for a program on the Google Play Store called “Torque Pro”.
I like your idea better*! Mine was to glue a mirror cut in the same size and shape of the gauge onto the dash, but have in quotes written in marker at the bottom,
“Oh…! Pretty…!” 
*****The OP would get punched less with your idea.