In my experience, it would be possible to use it as a document database, and I suppose it would be good in the interest of reducing duplication issues if you were initially storing the documents in a traditional DBMS or file system.

However, that's not really what it was made for. Especially early on when you're planning out your schema and such, dropping and re-indexing your documents is a really simple task. If the index itself is your primary document store, what are you indexing from? Would you have a DBMS or file system as your secondary store in that case? That just seems so awkward and backwards.

Keep the square pegs in the square holes and use Elastic (and the alternatives discussed in this thread) as a search index.

It might depend on the amount of data. We used it store 150 - 200GB of product data, and at that scale it was completely fine, just hard to manage.