Hi there! Thanks so much for your interest!
Technically, there shouldn't be a problem, as both the head/writing mods have ao3 accounts so they'll be able to view the application and judge accordingly. However, we can't speak for the entirety of the mod team having an ao3 account.

We would suggest that if you're concerned about other mods not having access (and therefore not being able to vote on your application) to make a Google Doc instead! Or submit a Google Doc, with a link to the ao3 from there.

Ultimately, it's up to you to decide how you'd like to handle it! We will judge it though, and won't consider it an invalid link simply because it's not publically available if you use the ao3 links. We hope this answer helps! Thanks for checking in with us about it.