(ET) Question for the EE types

[Charlie <medievalist gmail com>]

In at least three places in the Elec-trak's original circuitry,
voltage is being dropped by resistors which waste a portion of the
power as heat.

In theory, could a circuit be designed to substitute a less lossy
voltage converter (buck-boost maybe?) using the original wiring and
connectors?  A "plug in" replacement for that card full of resistors
under my dashboard, or a "bolt in" replacement for the toaster?

I'm aware that an Alltrax would make this unnecessary, but I've got a
late model I-5 in reasonably cherry condition and I don't want to
install a potted controller (admittedly if I had a field reversing
relay I'd drop in an Alltrax in a heartbeat).

--Charlie