The Upload widget would be vastly more useful if it could upload with the PUT as this would enable direct to S3 or GCS PUTs.
I am stuck on this as well (Amazon S3)
Anyone evaluating widgets who needed direct uploading to S3 should choose another widget. If PUTs are easy to add it would be a selling point for Kendo.
Upload to Azure Blob Storage would be possible as well, if PUT would be available.