A web framework where AJAX was not an after thought
Two approaches to this problem generally. One is for the framework to try and do it all, like Microsoft's ASP.NET with its Ajax toolkit. This includes server side controls that produce Ajax functionality with all client- and server-side code generated for you. For example, their UpdatePanel control allows for partial page updates via an Ajax call. However, it is not universally popular as a framework in general because their Page and Control models are sometimes seen as too heavyweight and overbloated.
A second, "slimmer" approach would be to separate the concerns. Let jQuery or a similar library deal with cross-browser inconsistencies and the client side of the Ajax call, and use a simple lightweight server-side web framework, such as Groovy on Grails or Microsoft ASP.NET MVC (there are others as I'm sure people will point out). Any decent framework should be capable of easily producing either JSON or XML data in response to an Ajax call.
As for browsers with Javascript disabled - this is the twenty first century. Do you really have to cater for them any more?
AJAX is a pain in the ass because it essentially means you'll have to write two sets of similarish code: one for browsers with JavaScript enabled and those without.
Not only this, but you have to connect JavaScript events to hook into your models and display the results.
And if all that weren't bad enough, you need to send an address change with the request, otherwise the user won't be able to "click back" correctly (if confused look at what happens to the address bar when you click links in GMail).
We're searching for something that had the foresight and design goals with all these concerns in mind.
Performance and security are also obvious major concerns.
We love config-based systems as well, where you don't have to write a lot of code you just drop it into an easily read config format.
It's like asking for the holy grail right?