Maybe an updated version of the book (and its examples) [1] would help? Or do you have some other concrete examples
It comes down to your resources: do you have the man power to create several default vcl files that people can "just use": like a vcl for a RoR app, vcl for a WordPress site, vcl for a Symfony app etc (depending on actual usage/popularity)...
I started using varnish because of this tutorial: http://ewan.im/900/10-million-hits-a-day-with-wordpress-usin...
I know it's a catchy and grabby title and sort of BS if you think about it, but it just works.
It took me an hour to get a DO dropplet running and blitz.io reported numbers that made me happy ($10 DO dropplet, large WP site, 27k+ requests per minute), that's enough for us.
I've got a few other ideas, but I think that if your company does something similar, you'll be able to get a much wider appeal and engage with users a lot more, which is great PR and marketing for your paid service.