JsonReaderInternalAccess.INSTANCE - ugly design

I'm looking a way to implement MongoObjectReader - something like JsonTreeReader but use mongodb.BasicDBObject instead of JsonObject. Unfortunally some map type adapters invoke JsonTreeReader.promoteNameToValue or execute some ugly code directly onto JsonReader.

I can't derive from JsonTreeReader since it's final. I can't override promoteNameToValue into other JsonReader descendant since it's introduced into JsonTreeReader.

proposed solution:
1) make AbstractJsonReader to remove JsonTreeReader.UNREADABLE_READER stuff
2) make promoteNameToValue member of AbstractJsonReader
3) mark JsonReaderInternalAccess as obsolete