Marketing: default CSS?

I was discussing Seaside with a customer. The guy came up with the, I
think, good tip that it would be worthwhile to work a bit on the
out-of-the-box experience. Default Seaside sites are ugly, and only a
light bit of css would help a lot (sans-serif font, sensible values
for h1, h2, ..., maybe a bit of background color on h1 - stuff like
that). As an added benefit, default sites would be "branded" -
recognizable as Seaside sites.

I'm not entirely sure how this could be best done. The main issue is
of course that someone should be able to remove this CSS in a very
easy way..