Update Multi-field Completion Suggester Weighting

Question

Given the following mapping:

{
  "index-name-a" : {
    "mappings" : {
      "properties" : {
        "id" : {
          "type" : "integer"
        },
        "title" : {
          "type" : "keyword",
          "fields" : {
            "suggest" : {
              "type" : "completion",
              "analyzer" : "standard",
              "preserve_separators" : true,
              "preserve_position_increments" : true,
              "max_input_length" : 50
            }
          }
        }
      }
    }
  }
}

How do I update the weightings of individual documents? I have tried the following:

PUT /index-name-a/_doc/1
{
  "title.suggest" : {
    "weight" : 30
  }
}

Which errors with:

Could not dynamically add mapping for field [title.suggest]. Existing mapping for [title] must be of type object but found [keyword]

Which makes sense, since the property is of type keyword and not an object. But I can't find the correct way to do it. Closest I could find in the docs doesn't seem to work if it's a multi-field.