I don't think too many decisions have to be made. It is more of a resources issue. Hamilton seems to be the only developer in this community that is actively exploring AJAX in OpenACS apps. He has committed a useful ajax package that contains a few open source ajax libraries. Any package that wants to use ajax just needs to install the ajax package, and add a link in their template to point to the ajax library they want.
Where decisions need to be made is whether ad_form should be updated to use ajax, and RTE to use ajax for auto-saves. In which case, we'll need to consider linking the ajax package into the templates package.
