Is there any reason to change the default name for a hot spot in CS6 unless you are planning to do some custom coding in Dreamweaver or some other program?
Is the Alt text field designed for visually impaired web viewers similar to what an alt tag for an image is used for?
There's no need to change the default name for a hotspot unless it helps you in organizing your Fireworks document. As far as I can tell, the name does not appear in the exported HTML file.
As for the Alt text field, I think you're correct. The text that you input here is added to "alt" and/or "title" attributes of the <area> tag, which is the equivalent of a link tag. It's probably a good idea to add a meaningful word or phrase here. If this were a text link, the text itself would serve to provide this information, but that's obviously not the case in this scenario.