That's incredibly inefficient. S3 has to be reliable and store the data in a redundant way. Filecoin will have to do the same because losing a host happens all the time.

Also S3 is incredibly expensive if you factor in outgoing traffic costs.

Buying 5TB consumer drives for 130€ and throwing them away after one month of usage makes more economic sense than using S3 for filecoin. Heck if you throw those consumer drives away after 12 months the storage cost will still be cheaper than glacier which you can't even use for filecoin.