NNTP support is definitely an idea I like, but I don't think it's important enough of a feature to require in the first version.
Well, keep it in mind.
There are probably only dozens of people who would use it.
I think you might be underestimating the number of people driven away by the web-only UI. Or the number of users you would gain if following the site were as simple as adding it to the aggregator they already check every day/few hours.
Speaking of aggregators, I would like to say that
the SMF support for RSS totally sucks. Not only do you have to hand-craft URLs (the UI does not mention it ANYWHERE), but it is flaky as heck and seems to merge various sub-boards into a single feed in randomly-chosen ways. Bleh.