I am currently working on implementing autocomplete functionality. So far I have looked into the following options:
Completion suggester. We would like query-time ranking such that we can e.g. base it on term frequency, which does not seem to be possible with the completion suggester.
NGram Tokenizer. If I understand correctly, this would greatly increase the index size.
match_phrase_prefix. Is described as a poor man's autocomplete, but returns a full hit list like a regular search request.
Are there any other options, or should I look into writing a plugin? Ideally, I would like a phrase suggester that not only gives spelling suggestions but also autocomplete suggestions.