Well you'd have to add some override table for the automatic codepage/layout
selection routines and add fallbacks and stuff. Don't really see why, that one
textmode game/demo that screws up then, well.
And the first step to get a correct keyboard response is getting the english
layout to work, it's troublesome bug tracking if the layout (dosbox) is correct
but some lower layer screws up.

The question is whether this is something to be handled by DOSBox or by the installer. As it is, DOSBox uses the same dosbox.conf no matter which platform it is running on. Maybe that is the wrong approach.

Vista installs seems to require output=ddraw.
Linux/MacOSX - is there a tendency to use output=opengl ?

Settings like that could be adjusted automatically by the installer.

Similarly the installer could fix the keyboardlayout=.... setting.