I had the same thought about separating resteems from originals lately, but don't you I think it would decrease value of resteem? Like nobody would want to see them anymore.
But I think bookmarking other posts in the separate tab would be useful (in addition to resteems). At least for me. Sometimes I want to resteem a post so all my followers will see it, and sometimes I just want to save it and read it later :)
The bookmarking like a pinned post would be very nice also especially for an intro post to appear first or something like Facebook has!