If that's the case then I suggest he tries Hakyll, which has a dependency system built in so that it only rebuilds what it needs when files change.
Hakyll looks pretty slick. I'll check it out for sure. Thanks
I'd be curious to read a post-mortem once you get the site back up.
Caching with WordPress.org is as easy to set up as Jekyll, if not easier. With W3 Total Cache or WP Super Cache, performance is roughly equivalent to a baked site being hosted by the same web server.
Edit: Oops, I lost, as he already said in another thread that he had WP Super Cache turned on. But it seems to me that 512MB would be enough if the web server was set up properly, and in fact caching was set up so the web server would serve pages directly.