@Roman – ah, now I see what you're getting at. In some limited testing just now, it *does* seem like a [plug Foobar.vst, 17] message to vst~ does in fact load the plugin, and then select program 17. Cool! Now have to go see if I can figure out how to get pattrstorage/presets working with this… BTW, an image of my patch above is posted below in case you're interested.
@broc – yes, that's the advantage of Andrew's suggestion – it allows you to pick up on when the vst~ object reports an error. This was especially important to me when developing code that scanned through a whole folder of plugins, to test their instrument vs. effect status (to be loaded into different umenus in my app).