Implement some HTTPOS features in TBB
http://freehaven.net/anonbib/cache/LZCLCP_NDSS11.pdf lists several hacks that can be done at low cost to defend against website traffic fingerprinting. Not all of them are easy for TBB: some involve TCP/iptables hacks. However, others are relatively simple and include things like randomizing the accepted encoding, asking for ranges in parallel, issuing dummy pipeline requests, and so on.