I have been messing around with this a bit and it can be done, but there are a few limitations.
For uploading to frame io:
Things may have changed since I tried last, but uploading to frame io can be done by setting up a watchfolder.
A few gotcha's
The watchfolder has to be on a local drive, not an external drive. A limitation by frame io.
The files have to be moved to the watchfolder after they are rendered. Frame io might start uploading before render is done. This can be done with a postrender script.
Not sure what you mean by scratch doing transcodes from frame io data.