I'd humbly suggest something I didn't see on the mod lists unfortunately... a good example is on the link below, where they have the row of buttons ending in the one for bigger text. The ease their design shows for enlarging text in particular I think might be the sort of touch that helps increase your audience.
I know it can be done in Windows, using several utilities, in the browser, and so on... So yes there really is no need to stick that sort of thing on a web page, except that some folks don't know how or don't want to bother etc... Just a small touch to make their visit hopefully more enjoyable.