If you have a clean disposable plastic cup fresh out of the package and a gram scale you can measure in that and pour it into your fermenter without any sanitation concerns. Then tape the packet shut for further use.
One use plastic. A small piece of foil does the job.
I like the way you think. However, the plastic cup can be used many, many times over. Hops. sanitizer. Drinking. Doesn't have to be "one use". Just sayin'.