Using "console=tty1 console=ttyS0" for booting generates a broken /etc/inittab, 
resulting in (c/p of a serial connection):

 * Bootoption for serial console detected:
 * Warning: console=ttyS... not specified as last console= option. Fall  [ ok ] 
to set up ttyS0/9600.
 *   Activating console login on device tty1 with speed .                [ ok ]
 *   Activating console login on device ttyS0 with speed 115200,57600,3  
[ ok ]00,9600,4800,2400,1200.
INIT: /etc/inittab[71]: id field too long (max 4 characters)
INIT: /etc/inittab[72]: duplicate ID field "T0"                          [ ok ]

Executing:

  . /etc/grml/autoconfig.functions
  config_console

then once again generates further broken entries in /etc/inittab. The code 
should handle the tty* options in the cmdline accordingly and has to be 
idempotent.