Will this be a live connection or extract?
This will a extract.
Have you tried an extract with all of the data in it for starters? Tableau is definitely able to handle millions of rows of data and does quite well when the data is extracted.
More to the question, there isn't a way to swap out data sources like that, but there are some other approaches we could take. But all will require quite a bit of extra work and maintenance, so I think it would be ideal to see if you can make it work with a single extract to start.