What I had in mind was dynamic, real-time power adaptive power:
The router starts in a user-defined low-power mode that was configured during the initial customer setup or manually re-configured at any later time.
I get close enough to connect.
It ramps up power just enough to give me maximum speed.
As I move away from the router, it senses that it needs to increase power and does so.
As I move closer to the router, it senses that and reduces power, but it doesn't drop it any lower than the pre-defined "low power mode."
If more than one device is connected, it keeps the power as high as needed for the device with the weakest signal.
To those saying "but if you move out of the range of the low-power signal and disconnect, you won't be able to re-connect unless another device is connected and by virtue of that connection, the router is still in a higher-than-low-power mode." This is true, and it is by design. As an option, the router could put a short delay in the power-reduction to account for short disconnections.