This is an agricultural product. If you have cuttings and all go through the same highly controlled conditions for growing and processing... Yes, you will have a high quality control.
However, this a highly fascinating plant with many aromatic compounds being produced. It would be quite an extensive project to produce enough types to deal with every condition. There are some phenotypes in varieties that do not provide appetite stimulation, there are types that make you tired, awake, etc.
I think it should be kept small, growers knowing their patients and working to have varieties available that help them the best. Maybe collaboration with other growers to help too. Its such safe medicine that as long as they aren't using dangerous chemicals in growing the plant... There is no reason to involve standardizing the actual plant.
Yes. The quality of Medical Marijuana can be controlled if it is legalized. Marijuana would be under the same rules of government standards as alcohol is. Also Medical Marijuana would be supervised by the FDA just like the drug companies, falling under the same guidelines as other prescription drugs. This will insure the quality of the product for medicinal use.
No, the quality of medical marijuana cannot be controlled for uniform strength and purity, because marijuana is not massed produced. Marijuana is mostly made by people who run small grow operations, or by criminals in other countries who smuggle it here. With the production being so underground, there is no way to regulate anything that goes into the production of marijuana.