Is there a way to toggle the "request-password"-flag in the trezor without reinitializing it?
As no-password results in the same wallet as an empy password it would be nice to be able to switch between the settings (without having to generate a new seed).
What makes you think that the "no password" is the same wallet as an "empty password"? I doubt it is true. If you switched that flag, you would probably loose access to your "no password" account. Just reinitialize the device with the passphrase enabled.