That's a clever idea, and if it works for you, great. In fact I think it's a much better use than PowerPoint's intended purpose of crushing your soul bullet point by bullet point: http://norvig.com/Gettysburg/sld001.htm
It looks like you can sort of do this in Google Presentation too, though you have to figure out the URL to link to other slides.
Yeah, I have a feeling most presentation tools (Keynote, Impress, Google Presentation, etc.) would work well for this. In fact the only pain point I've ever had was the occasional desire to change the slide size. I've found that most of the basic effects in PP have a CSS equivalent as well, a surprising number of the things mocked up in PP can be recreated entirely in CSS without images.
Most of the actual graphics I use in the mockup I've made in Photoshop anyways, and just put them in the mockup, so those are reusable art assets on the final page.
(plus you can even mockup smaller gui details like drop-down menus if you are clever enough, though it's usually more work than it's worth)
I've found that most of the MS-Office tools can be abused to do a pretty good job in roles far removed from their original intent.
If you aren't already familiar with LaTeX, it takes some time to get into it. But it's definitely worth the effort! I know a lot of people who, once they started to use LaTeX-Beamer, never touched Powerpoint again.
To get a feeling of what LaTeX-Beamer is all about, you might want to have a look at the following tutorial (PDF):
It looks like you can sort of do this in Google Presentation too, though you have to figure out the URL to link to other slides.