From testing, it looks like we can do that! Except you need to pass the constantID, not the game object itself (even though there is a SetValue(GameObject obj) function for ActionParameters - didn't work for me when I used it like above.)
What if we want to cleverly avoid needing an in-scene interaction per hotspot by having them instead send a message to the script on the affected object, which then calls the global action list... but with public variables exposed by the script pass…
Figured it out - UniMerge puts a copy of each scene in the same hierarchy, which causes a duplication of IDs and makes the version in the "mine" column always generate new IDs.
If UniMerge is the problem, and you have a compatible way to merge, we aren't tied down to it. We use UVC (which uses svn) for version control and UniMerge for scene merging.