Clandestino;
Could you provide the reference that states latching of ALT2 permanently disables the autopilot?
It has been posted a number of times, but it was
takata in
AF447 - Thread No.5. I think
A33Zab has also had something to say on the latching of ALT2B.
EDIT :: If you are looking for an AI definitive reference, then I have not been able to find it in FCOM or Instructor Training Manuals, so assume that it will be hidden somewhere in the AMM.