An OLR would be great. You wouldn't need to invent a new protocol - you could use NNTP or IMAP or suchlike.

LJ also needs to dump skip=15 in favour of start=1102262910 or similar, specifying a start time, such that the starting point it represents is fixed rather than changing as new posts are added. That would solve the problem you present - and give you a way to say "give me all posts from this time onwards" facilitating the cookie thing mentioned above and similar possibilities.