I've seen my share of stuck oil pressure sensors (usually stuck
in the "good oil pressure" setting and I've also seen more than my
share of problems with wires (oil pressure sensor wire runs right
past several things that can melt the insulation and short the
wire to ground, resulting in a "no oil pressure" looking situation).
Either event is not good, and running the fuel pump off this wire
seems less than perfect.

In my mind, the pierberg pump is the best option in terms of
low complexity, quiet and failsafe operation and performance.

Clearly your setup is good in almost all situations and if you
use good materials and correct wire routing you won't have any
problems at all. If you need a different fuel pressure range than
the pierberg pump delivers your setup may be the only game in
town and is certainly a better setup than I've seen elsewhere
where the fuel pump is simply run off of a circuit switched with
the ignition key -- a fiery disaster waiting to happen.

Fuel injection systems have a relay to the fuel pump that is
operated by a computer sort of thing that senses when the ignition
has stopped firing and stops the pump (Except in the "start the
car" condition". With webers this isn't an option. And, I think
old mechanical fuel injection systems had the pump driven off
of the motor, like a diesel.
chris