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Dear John:

Lots of interesting ideas.  My comments:

1) Bob Nucholls makes a powerful case for avionics switches being no longer
necessary given the TSO requirements of modern radios (they must tolerate
input spikes) and the widespread of use of diodes around relay coils to
trap transient spikes.  I believe him.  Old traditions die hard.

2) Remember: every additional goodie you add is a potential failure point
that will probably fail, but only when you are in deep do-do and really
need the juice.  If you really want thermostats for pitot tubes and
such, I recommend a bypass switch so you can heat the thing when the
thermostat decides to take the day off.  Goodies are nice, but if it
is not installed, it can not fail.  

Keep thinking about what happens in the event of a failure, and you will
migrate to 1) simple is beautiful, and 2) redundant is pretty good
looking as well.

Failure analysis shows that putting elements in series rapidly increases
the probability of a system failure, but putting redundant elements in
parallel diminishes the chances of a failure.  

KISS.  (Take it from one who has learned the hard way.)  

Fred