FCKeditor might not be the right tool for that task, but your XML doesn't use self closed elements, so in the end you might be able to do it.
The main problem is that the source will be parsed by the browser, so that source must be properly parsed without messing with it and self closing elements are usually the weakest point.
Start using that XML inside an html document and try to use a stylesheet (CSS not XSLT) to display that content as you want. If you are able to do that, then you can keep on trying FCKeditor.
But then, creating elements like it's done with the Bold, Italic.. buttons will be harder, at least by the moment. Once 2.5 is released (it's getting delayed a little...) it might be easier, but you are always on the edge of what's possible and what's outside the scope of the editor.
Re: How to create custom XML using FCKeditor?
The main problem is that the source will be parsed by the browser, so that source must be properly parsed without messing with it and self closing elements are usually the weakest point.
Start using that XML inside an html document and try to use a stylesheet (CSS not XSLT) to display that content as you want. If you are able to do that, then you can keep on trying FCKeditor.
But then, creating elements like it's done with the Bold, Italic.. buttons will be harder, at least by the moment. Once 2.5 is released (it's getting delayed a little...) it might be easier, but you are always on the edge of what's possible and what's outside the scope of the editor.