* Generate one html file containing everything
This is easy, just use the monolithic flag.
* Configure the navigation panels
It seems that texi2html.init file gives some room for
configuring how to generate the navigation menus. I think
you can put them off, but well, it is my *first* look at it.
* Allow some configuration of the heading of the generated html file
Although this seems very limited I am not sure if you can use this
to use the stylesheet.
I could take a look at point 1 and 2 if you think it is an improvement.
Point 3 as well, but I have never used any stylesheets before so
this would cost me more time.