Hi Jules,
Since you provide a means of scanning for plugins on a different thread, would you mind also providing a macro for turning off the following assertion in juce_VSTPluginFormat.cpp?
#if JUCE_WINDOWS
// On Windows it's highly advisable to create your plugins using the message thread,
// because many plugins need a chance to create HWNDs that will get their
// messages delivered by the main message thread, and that's not possible from
// a background thread.
jassert (MessageManager::getInstance()->isThisTheMessageThread());
#endif