Prepare for some harsh feedback.

You need to think about the national screening committee. Will they want to fund a project that is fully thought out or one that is very general and unspecific? Who will they think is a better candidate to invest in: one that spent time developing a project and clearly articulating its methods, goals, and possible problems and solutions? Or one that doesn't seem to have spent much time thinking about the project at all and just wants to "go with the flow"?

For research and study projects, there is a much higher bar for applicants. You won't get it if you don't seem serious, and saying things like "I'd rather keep it general and then see how it evolves when I get there" doesn't show me that you've really invested yourself in the project, that you've really thought about what your project is and what you can expect when you begin researching.

You'll be going up against undergrads who spent their entire junior and senior years studying their topic. You'll be up against graduate students who are doing a dissertation on their Fulbright topic. You need to be as serious and competitive as them.

Fortunately, you have a few weeks left to revise your application, so don't panic if you think you're not at all ready to submit.