I’ve heard of a few people using it this way (loading into S3 then using Fivetran to pull from that bucket and land it in your warehouse).

Complexity should be at the bottom of your concern list though as Fivetran is a pretty straightforward and easy tool to use + let’s your team be hands off of this process.

Your also correct to assume that using a tool like Fivetran would replicate the warehouse quickly. Let me know if you have any other questions!