Is it possible to emulate ISO/IEC 15693 cards on Android? According to my research Android currently supports read/write interaction with ISO/IEC 15693 cards, however I couldn't find any info on emulation. If the emulation is possible would it require secure element or/and HCE?
No, Android currently does not offer any API support for ISO 15693 host card emulation. Devices that support UICC-based card emulation over single wire protocol (+ HCI) might support proprietary(?) extensions to make the UICC emulate ISO 15693, but this is typically not the case either (note that this would be device manufacturer specific and beyond the scope of what AOSP currently provides).