Proposal: Implementation of a "signer" app (Android/iOS)

I would like to propose the implementation of a separate "signer" app (Android/iOS), along with decoupling the cross-signing/verification/security logic from the chat app logic. This type of decoupling can be seen in the banking sector.

This would increase the usage flexibility and cover scenarios where the user is primarily using a web client (e.g. Element Web) and only wants to install a lightweight app for cross-signing/verification purposes, rather than an additional full-fledged heavyweight chat app on top of the 6 other chat apps already installed on the phone.

This app would include features such as cross-signing/verification, QR code scanning, access via PIN or fingerprint, support for (signing in with) multiple accounts etc.