Calling methods from Sibling Components

That's fair. Out of curiosity, then, is the main driver towards the project library at that point the fact that it's cleanly versionable and maintainable as a separate resource?

That is, in a perfect world where legacy concerns like the scoping in gateway event scripts weren't a problem, would you still advocate pushing all logic into the project library? In my (naive, never-had-to-deploy-an-actual-Ignition-system) head, I would have assumed that locality of "presentation" logic (i.e. on the view/component/etc) would be generally preferred to going all the way out to the project library; if nothing else than for a nicer editing experience within the Designer.