Hi Jonas.
It is possible to add Extension X3 to an already existing site. There are no limitations or anything else by not using it from the start. So just change the inheritance/add the ExtensionPageHandler on your existing page templates and add a Content Area and they are ready to go.
The only thing that is needed is that all existing pages where Extension X3 is added on afterwards needs to be resaved before you can start adding content on them. This is something that can be avoided by running a script. Just send us an email if you need it.
We also have a beta version of a "Convert EPiServer pages to Extension X3 pages with functions". Just send us an email if you need that aswell.
Any further questions? Den't hesitate to ask.
BR
Fredrik Karlsson
Dropit/cmsapps.net
Is it possbile (or recommended) to add X3 on a current site built in CMS R2? Are there any problems by not using it from "scratch"?