I have been an adjunct faculty for a number of years and I still don't trust some of our own dental students performing certain procedures (under the proper training), let alone a dental assistant to scale our patient's teeth. 

Not using a scaler correctly can cause harm to the patients.  I wouldn't want to support this as it would not be in our patient's best interest.  Many of my patients with whom I have spoken to with regards to this matter do not feel comfortable and opposes the idea of having "an assistant" clean their teeth.  Polishing is okay.