I've heard that Heritage might not be what it used to be, and that
Madera Concepts might be better.

Problem is people don't understand how thin the veneer is... otherwise, it
becomes plywood looking.

I have had a lot of experience with varnish on boats, and would follow
your suggestion if I could depend on the finish standing up to
exposure.  Unfortunately, varnished wood exposed to sunlight for long
periods (if you have a convertible the top is almost always down, even
when it's cold) requires periodic attention and touch up.

Removing the console cover requires pulling the radio, AC, and gear
shift, and is not the sort of job I would like to have to repeat every
year or so.

Canoli  

Good point. However, one other step is necessary to prevent it from curling
forward from end to end. After straightening, seal the back with epoxy. The
reason you want to do this is to seal the back from water vapor. Epoxy is a
100% solid while varnish is not. Also, do not use polyester resin. It is not
a 100% solid product. What you smell when applying polyester resin is the
styrene gas escaping from the matrix. As this escapes it leave little hollow
trails for vapor to penetrate. Epoxy prevents this from occurring. The 5 or
6 coats of marine varnish will work on the front but I would consider using
a good polyurethane instead. Make sure you use the gloss type as no amount
of polishing will bring a nice luster to the satin grade. Also, if I were to
finish a trim strip myself I would strip the original finish and avoid any
unnecessary sanding. I would then wipe the stripped wood trim with a moist
rag and run a hair dryer over it. You can use a heat gun IF you are very
careful not to burn the surface. The reason to do this is to raise the
"hairs" of the wood for sanding. I'd use nothing more coarse than 600 grit
for this, probably 800 to 1000. Repeat a couple of times. Then I would
finish both the front and back with a good polyurethane such as Deft. Three
or 4 coats I think would work fine. It's important to get enough material on
so you don't polish through the finish, back to the wood surface. I have a
little finish trim spray gun that I'd use for this work. Hummmmm.....maybe a
profitable past time finishing MB wood trim.......hummmmmm.
One more thing is to make sure the wood strip is straight before you begin
work on the finish. If it's not you are going to be disappointed with the
results. If you have a curl in the wood you can easily straighten it by
laying it down on a damp (read wet) towel with the bowed side facing up.
Place it in direct sunlight for several hours and draw the moisture out of
the back side. This will pull it straight. Careful, you can actually bow it
in the opposite direction if you leave it in sunlight too long.