I already had a look at the Reading List Plugin, but at least right now it also does not seem to allow such a kind of filtering.
I have to disagree regarding storing no data on the main memory. In my experiments the internal memory got filled up to 100% (and I have no idea how to clean that up). After a factory reset, on an empty Kobo Glo, I had 1332 of 1361MB available. After copying 220 books on the reader 1266MB remain, which means somewhere are stored, on average, 300K worth of data for each book. And since the books are, on average, larger than 300K it won't be the whole book. When I looked at the mounted volumes, though, there was next to nothing on the internal memory.
This limits the number of books that could be copied even on an arbitrarily large sd card to something around 4.000 books.
Btw., I'm using 2.5.0.