But I want a more Ajax approach to it by sending the request to the server when the tag is to be rendered.
Is it possible to make such an implementation using Ajax in JSF 2.0?
I do it all the time. Just indicate that AJAX is to re-render the field(s), and have the AJAX-invoked server-side method set properties that can be queried in a "rendered=" attribute EL expression on the fields being re-rendered.
An IDE is no substitute for an Intelligent Developer.