downside: entity appears twice in search results
variation: Take a snapshot of the entity's JSON
downside: cascade delete counteracts immutability (but might work around by walking tree upon move or delete request and stopping if published entity is descendent. This has other repercussions, e.g. locking down an entire tree)
downside: lose context (but maybe can recreate using references or Activities)
downside: only annotations and data file are currently versioned
Fundamental question:
Does the wiki actually need to be immutable? If not, what IS it that must be immutable, just the referenced file(s)?