Thanks. My first question was in fact the one that mattered more to me. (I just couldn't seem to stop myself from going on to the second.)
I also appreciated the comments by rchiavo and hardburn, who hit the crux of the matter pretty well: I confess to having been clueless about the mechanics of plugins, or how they would benefit from a design that says "load whatever exists in this path", and I should have just started with curiousity instead of criticism.
But your reply was the first one to give some clues about plugins (which are still somewhat mysterious to me), and I'm grateful for that.