Rob:
You can run multiple VE2 standalones addressed through the IAC ports. To do this, duplicate and rename the new VE 2 app. or apps. I don't know whether Sibelius allows you to run plugins and standalones simultaneously, but, if it does, you can run 2+GB of plugins within Sibelius + one or more VE 2 standalones
The only problem with standalones is that you then need to have some way of looping their output back into your computer. If you have an RME or an Apogee Symphony card based interface this can be accomplished with the software that comes with these interfaces. If you have an interface that does not have this capability then you can use a DAW such as Logic as an intermediary application.
For example, my notation program is Finale 2008 and I have a MOTU 2408. I set Finale to address Logic through IAC port 1 (channels 1-16) giving me 16 channels in Logic itself. IAC ports 2 & 3 are assigned to Channels 17-32 and 33-48. I then run a short ADAT cable from the output of the 2408's Bank C to the Input of Bank B. Then I assign the MIDI inputs of each standalone to the appropriate IAC port (e.g. Port 2, Port 3, etc.) and the stereo outputs of each standalone to the appropriate audio channels in Bank C (e.g. channels 17-18 for the first standalone, channels 19-20 for the 2nd standalone etc.) Then I create AUX channels in Logic whose inputs are channels 9-10, 11-12, etc and whose outputs are channels 1-2. Logic has a "Helper" I/O plugin that greatly reduces the resultant latency when inserted into the AUX channels.
I know this sounds complicated, but it does work. Of course, once there is a 64bit OSX version of VE, this workaround should not be necessary. Hopefully, this will be reasonably soon.