Speech-language Pathology student here. I would recommend going to see a speech therapist. It will likely be covered by your health insurance. Find an SLP who specializes in AAC (Augmented and Alternative Communication) who can help your wife communicate if she loses her speech. Your DIY approach could work, but having support from an SLP to help her learn the system, and come up with other options if it doesn't cover all of her communication needs, will go a long way.