Fencer:
1)Yes Ajax is not universally suported but is almost.

2) If you encapsulate the different parts you want to update into there own subroutine then use javascript to update each you can have it put out raw html witch would require few changes to the sight.

3) Overhead of using noscript is very minimal. If they have scripting you put in the ajax code set to run every 30 sec. If not then you are still using the same subroutines to create the page just not adding the extra java script to allow it to reload in the background and using the meta reload instead.

It is a little bit of extra work but the visual improvement of not having to reload the page as well as the bandwidth reduction by not downloading parts not used would vastly improve this site.