As you are mulling over features for inclusion, here is my suggestion.
It is based on my usage pattern, but I think might apply to a lot of folks, and I wouldn't think would entail a huge amount of work.
The way I most use GrazeRSS is that on my walk to the station, I go through my feeds and pin a small number - typically around the 10 mark - of articles that I want to read the web page of. Then at the station I resynchronise, and then on the train I will read what web views I can before I lose coverage (my train runs through a hill range that has no coverage at all).
My idea is that upon sync, an article is pinned has a different download type to what it has otherwise (maybe the pinned-article download type can also be per-feed) so that I can get just the feed content normally but those I decide that I want to read based on looking at the feed will get downloaded fully next sync.
Net result is that I will have a mix of things I have never looked at for which I have just the feed content, and things I have marked as wanting to read fully, for which I have the full web page.