Without the "model=acer" option passed to snd-hda-intel detection of insertion of headphones or mic doesn't work on at least the Acer TravelMate 5720. s-c-sc should add this to modprobe.conf upon detection. Aside: Perhaps hal can/should be used to store module options based on the machine/hardware info.
It has to be done by upstream (ALSA project). We can't keep info about all hardware devices.