I too suffer from TMSPS (too many side project syndrome). I have a feeling the interface forums needs to form a support group for us.
Suggestion I have regarding, would be to look into the addon authoring of some of the major IDE. There are many out there that already handle xml editing, syntax highlighting, and completion (if you include dtd or xsd support for your xml structure). The addon portion would then simply be a translation component for "export" or a preview type panel. I'd been looking at writing simple lotro api context support library for Eclipse, but got bogged down in TMSPS yet again.