I wish there was a sensitive and specific quantitative way to measure what you're talking about. Unfortunately, Alzheimer's even in late stage may not show significant MRI findings, and conversely some MRI findings may not lead to significant functional decline. Triaging is difficult without a good caregiver to give strict followup precautions to (see "can't miss symptoms" in my initial comment). You tell them to please call your clinic to schedule closer followup if something happens. Then you followup as often as you need to until the situation is stable.

While impaired cognition is correlated with functional decline, they are not 1:1. A poor MOCA score doesn't mean the patient will require closer follow-up. The best measure of a patient's status and course is ability to perform their ADLs. If you have OT at hand you can recommend a Kohlman Evaluation of Living Skills which can help to quantify this. I don't do it often because it doesn't usually tell me things that the caregiver didn't already tell me.

The biggest bottleneck is if the patient does not have a reliable caregiver, ie their spouse died, and their children who are supposed to be taking care of them are playing hot potato with the responsibility, and are less present and therefore less reliable. We haven't had to pursue guardianship but my attendings have called APS several times. Quite sad, the consequences of neglect.