If the VST Tempo/Sync problem was fixed you could use an external VSTHost so BB/RB is not all doing the work and crashing, VSTHost can use a VST/i plugin Legree.dll/Legreei.dll (VSTHost Slavery Suite) that would sync BB/RB with the VSTHost64 without latency.

http://www.hermannseib.com/english/vsthost.htm

May be PG could make a 64bit VST Slave Host without a total re-write ?

Sure BB/RB 64 bit would be great but it is a massive re-write $$ undertaking for PG at the moment, but who knows they might be working on it now.

You can try this with Live Professor 64bit Host, but it just uses midi clock at the moment.
http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=308107#Post308107