Hi JarJarThomas,
What you're describing is almost an "evil twin" scenario.
Plastic identifies items (files and directories) with "unique item ids", so if you add foo.c to /main/task001 and another foo.c to /main/task002, they'll show up as different items because plastic tracks them independently.
This way of working is pretty good for most situations, but as you mention not as good for an scenario like yours.
But, in real life, it is hard to see a situation like that. The normal thing is that you add your code on the /main branch (for instance) and then you branch from there, and adding whole new trees on branches is perfectly doable, although it will be very rare that they'll collide.
pablo