I'm not familiar with Ridgeside, but the way this mod works is very simple, so it should be doable. However, you would need some sort of "first-meeting" event with those NPCs to transfer the friendship points, but adding one yourself wouldn't be too difficult either. That is, if you want to stick to Content Patcher, with SMAPI you probably wouldn't have any of these limitations, but I'm not familiar with C# personally.
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"UpdateKeys": ["Nexus:13221"]
If you update the mod, then people will get notifications. As of right now, SMAPI gives a debug message about the mod not having any update keys.