It would be local if the mountain weren't there.
Agreed, but what if you don't own the mountain? What if this were an urban setting and rather than a mountain the object blocking transmissions is a building, which you don't own?
I understand how a bunch of repeaters connected by a bunch of links could cause problems, but in this example the objective is to maintain a normal transmission range, not to spread RF over the continent. What's the downside?
Simple wording: "A GMRS repeater shall not be linked to more than one other GMRS repeater."