So I'm unsure I understand what problem do you have with elasticsearch.
I mean that if you save all that information using a JSON document, then _source field is stored exactly as you send it...
If my answer is incorrect, could you provide a full recreation script as described in About the Elasticsearch category. It will help to better understand what you are doing. Please, try to keep the example as simple as possible.
A full reproduction script will help readers to understand, reproduce and if needed fix your problem. It will also most likely help to get a faster answer.