If you are not in X and already at a virtual console, you do not need to use Ctrl and just Alt+F1 should work. If the keyboard issue is that it cannot handle 3 modifiers, this might help, but if the issue is that the Function key doesn't allow modifiers, then this won't help.
To get around this, if your keyboard has arrow keys, Alt+left/right arrow keys should cycle through virtual consoles.
If that still fails, you can use
chvt(1), which you call with the form
$ chvt n
where n is a number for one of your virtual consoles. This allows you programatically to switch consoles without need to any special keyboard input.
Finally, if you want to completely change the shortcut, you can do this with
loadkeys. From a virtual console you can run
dumpkeys to output the keymap and you will see entries like
keycode 59 = F1 F13 Console_13 F25
alt keycode 59 = Console_1
control alt keycode 59 = Console_1
which defines keycode 59 as F1 and then defines Alt+F1 and Ctrl+Alt+F1 to "Console_1". You could change the last two lines to
alt keycode 2 = Console_1
control alt keycode 2 = Console_1
keycode 2 is 1 (from
dumpkeys output) and then load the modified keymap with
loadkeys, and now you should be able to switch console 1 with Alt+1 or Ctrl+Alt+1