i don't know if 'old browsers' is the target market, unless there's some funny niche somewhere that can't upgrade their browser.

maybe a neighboring idea would be creating a proxy for low-bandwidth devices -- e.g. transparently compressing/downsampling images, CSS, JS, HTML so that browsing on EDGE is a little more bearable with an iphone or other mobile device. (this might already exist, but i haven't heard of anything like it)

although i guess that wouldn't really use your imagemap hack or screenshot tool :)