I just uploaded a new plugin I did. It is called "EncodingPlugin".
It provides you with an option to select a charset encoding (UTF-8, ISO-8859-1, ...) but at the project level, as opposed to the IDEA IDE-level setting. It does not though, actually change the charset encoding when opening a project. This is still not possible.
What it can do though, is warn you, or someone else opening the project, if the IDE-level charset encoding and the project-level charset encoding does not match at project open.
Full release notes can be found here:
Would like to hear if you find it helpful.