SFOS Privacy and Security is excellent. Security could be enhanced in the future by supporting Secure Elements (SE) or even API for Trusted Applications (TA) inside a Trusted Execution Environment (TEE). A piece of hardware (smart card) or secure enclave (TEE) might be very useful for the security even on a mobile, for applications and the OS itself. (IPsec/OpenVPN, GnuPG, S/MIME, random numbers, FIDO U2F, trusted user interface...)
a)Support for SE with OpenSC https://github.com/OpenSC/OpenSC as middleware, PC/SC and a CCID driver for a smart card reader; there are a lot of use cases with OpenSC support and a lot of supported Secure Elements (e.g. OpenSC PKCS#11 Smart Cards are widely used on linux desktops, rasbian too) Could this work in practice with a mobile, with the opensc minidriver and read only PKCS#11 card access, e.g. with SDCard or NFC support?
vevgenievtried access with the browser https://together.jolla.com/question/132416/using-certificate-on-hardware-token-in-browser/
...complex or not working?
b)Support for SE with Open Mobile API http://simalliance.org/wp-content/uploads/2015/03/SIMalliance_OpenMobileAPI_v3_2.pdf maintained by GlobalPlatform https://www.globalplatform.org/specificationsdevice.asp (includes support for SE like UICC Applets, ASSD SDCards or embedded SE)
seek-for-android is an example for the Open Mobile API and can be implemented by the handset vendor because it is not a part of AOSP http://seek-for-android.github.io/
c)WebAPI for Accessing Secure Element - a new approach http://globalplatform.github.io/WebApis-for-SE/doc/
d)TEE client API for access to Trusted Applications (TA) inside a Trusted Execution Environment (TEE) https://www.globalplatform.org/specificationsdevice.asp (e.g. TEE secured by ARM TrustZone and provisioning distributing TA by a service provider with Trusted Service Manager (TSM))
...very complex, indeed
SFOS developers - are there other (simple) possibilities or are there already solutions (using the other half and I2C)?
EDIT: tag changed from feature-request to idea; lots of minor changes