The plugin situation is particularily bad when you need to open an old example file that uses a plugin or behavior that is no longer available on the web. Construct2 has no way of dealing with that and completely locks the file from you when you dont have the plugin - even if the plugin is not being used in any important way in the file.
The only plugins that do survive (or have a relatively better chance of survivng - some of them do get discontinued) are the ones that tend to still work.
I think the repository is a key element here. Without a repository, you have users posting plugins on weird hosting websites - with many links going dead after a while - dragging a plethora of capx study files to the grave with them.
1. Construct needs and official repository - plugin manager to update and download them - possibly even integration with the store
2. construct needs to have a way of dealing with scenes with missing plugins - let the user open the scene - but lock the parts of the logic that the plugin has on the event sheet - until the plugin is installed