So if I entered "password1", I get my normal files. If I get "password2", I see limited files, or special files, or a different user's files.
Beyond that, find programs you can edit files and add a wrapper ontop to demand passwords. Once you have something you like then can expand. Can do it in shell/script easily enough, though depends upon exactly what you want.
No point in having one program that caters for your editing when another program outside those controls is just as accessable. So with that you won't want to to be rewritting edit programs.
Another option would be looking at source code control SCC systems, may be a handy repository that would enable the control (and more) you may want, also get version control ontop which raises the area overlooked - auditing. If somebody changes a file, you may want to know who later on and why.