Like Bucket and Rocket, shore it up. I did this on one of my old houses. I'm not sure about supporting it from the wall studs. I put jacks on blocks under the joists and lifted the corner of my house about 1/4" to give space to remove all the rotten material and replace with new. While I was at it, I added another 6" course to the foundation because earth contact was the main cause of the rot to begin with.

Sg