In an ideal world, you would simply take the revised list of content and go create it. However, some of the content that users will want may be impossible to provide.
There is also the issue of competing sites. If there are other sites providing basically the same content, how will yours be better?
If you cannot provide some of the content that users will want, you need to consider the best action. You could:
- link to the content elsewhere
- continue as planned, but without that content
- stop trying to cater to that user type
If you continue without the content, you need to be sure that the content you do provide for that user type is sufficient for them to get something out of your site.
If another site provides exactly the same content as you are thinking of providing, or better, then unless there's something particularly wrong with that other site, there's no reason for you to continue.
An awful lot of Web sites suffer from "ok site, but this other site does everything that it does, and more" syndrome. There's really no point in having these sites on the Web at all.