I know this is slightly off topic, but it would seem only natural to me to actually place a feed reader in the browser itself - actually have browsers that have smart UIs and are more than just fast javascript processors and rendering engines.
But seriously, you're right that the challenge is in actually designing a good UX for yourself. You've got four months to mimic Reader if that's what you want to do. I'd suggest XSLT, since RSS actually predates JSON, it's so old. That doesn't allow for any potential mistakes by RSS creators, though, which might be hairy. /shrug
Syncing history - could help regarding your reading history (privacy aside.)
Coupled with an 'easy read' mode in the browser (I haven't tried Safari in a long while,) might make for a pleasant experience.
Non of the popular browsers have a good Bookmark UI IMHO, which leads to inappropriate tab use.