Well, color me surprised, but after getting the phone back in an almost normal state (Android flashed back on it with the official image from Fxtec - and a 99% broken fastboot implementation in the bootloader), my phone actually has it's IMEI still intact (The one I see with *#06#*, I haven't tried to check the second one yet) and everything works as it should, so apparently it is possible to overwrite the persist partition without any issue ??? 🤔