Depending on a variety of factors, the water which reaches the ground beans in a percolator can easily have a temperature above the optimal brewing temperature, which can result in over-extraction, and ruined coffee.
What if we made a percolator which had an upper cold water reservoir, along with a thermostatic tempering valve, to mix that cold water into the hot, so that the temperature is precisely what the user desired.
The valve's output temperature could be selectable, by the user, from anywhere in the range of 92 - 96C (about 176 - 205C).-- goldbb, Sep 25 2011random, halfbakery