What you are describing is going to be nightmare to work with - i.e. when you will have automatic detection of levels and it will decide to push RS232 into 3V3

What you are describing is going to be nightmare to work with - i.e. when you will have automatic detection of levels and it will decide to push RS232 into 3V3 MCU then you will have dead, maybe one of the kind prototype or dead expensive production device