Is it a good idea to fragment your banner into mulitple bits that are linked to different locations?

To answer that, the first thing you need to know is whether this will work in the different email clients. Lets look at image map (what is?) support across the most popular email clients:

Windows Live Hotmail no longer supports image maps. Curiously, Gmail now supports image maps in Safari, whereas it didn’t before.

Accessibility and image blocking issues remain the same

Despite the results looking relatively rosy for image maps, we still discourage their use for the same reasons as before. Image blocking in email clients continues to be commonplace and thus image-heavy email newsletters are as problematic as ever. In addition, image maps still make life tricky for the visually impaired and folks who read the plain-text version of HTML email newsletters, as the links display without context, if at all.

Our recommendation is to avoid using image maps altogether.