Incase anyone views this !!
Approach I am taking

UX

→ have a custom page on beacon live admin for each site
→ the user can upload 3 files

1. input xml file definition (input_config.xml)
2. maps xml elements to beacon components, slots, attributes and hooks (mapper.xml)
3. input data exported from WordPress or from an existing beacon site

Unresolved points

→ multi media migration

Technical details

→ use Beacon.LiveAdmin.PageBuilder for UI, this also simplifies life as we get access to live_upload
→ a Dynamic supervisor and registry with name being site name for maintaining state
→ SAXY for parsing of XMLs
→ Utilize Beacon.LiveAdmin.Client.Content to make changes to actual site

Other considerations

→ dropping input config file keep only mapping file less robust can still be “extended” for handling different versions/formats other CMS platforms
→ hardcode WXR quick to get up maintenance nightmare

Any solution should eventually be able to import/export to format of users choice

Any feedback and suggestions are welcome

Just because this recently crossed my path: Wordpress has an ongoing effort to make import and export of its data as transferable as possible. I didn’t manage to find much of a specification in my ~2 minutes searching the web though. It seems that format wise an export via “WordPress eXtended RSS” (wxr) you mentioned still seems the current way to go.