Using Chat as a Game Input and Custom Chat UIs

I plan to have parts of my RPG game use in-game chat in order to progress. For example, there is a magical barrier that has a password which must be spoken in chat. I see an issue with this, since there are players that have chat disabled.

Since I think my game needs a custom chat UI anyway, I am considering how I can use it to allow players with chat disabled to progress. I think what I will do is make these players able to type messages, but these messages are not seen by other players, only the server. And they will only see messages that the game sends to their chat UI. And don’t worry, the chat will be filtered.

Do you guys see any potential issues with this?