First off, the scene I'm trying to create is like the Burly Brawl from The Matrix Reloaded. There are a lot of figures, in many different positions all interacting with each other, so simple replication is not a solution. I'm not sure if proxy is the right term, but what I'd like to do is have very simple, low-rez figures that I can position in the scene, that will then be replaced by the real figure at render time. Could this be possible through scripting (which I know nothing about, sadly), or might this be more a thing for one of the pro programs like Max (assuming Max can do it)?

There is a plug-in for this around some where... but for multiple figures, and without the plug, try 10 different poses of the same Agent Smith, and use the replicator - I've had success with five poses of a bird, then replicated in a flock flying - I even used animation. You're looking to make an animation or just a still?

Inagoni sells Replica and Swap - check that out too.

Thanks, I'll look into those!
At this point, it's probably just going to be stills, but with figures positioned far above the ground, as well.

I think the Inagoni Swap plugin should be ideal.

http://www.inagoni.com/content.php?content.6