A new way to secure the app?

Currently, I’m working on a web app for the finance company that runs on just LAN. My client wants me to be innovative when it comes to web security. I have developed the app with node.js and react.js.

I have already used Bcrypt to hash passwords. My client wants something more to enhance security. I have no idea what to answer him. I will be grateful if you could just share something on this!