Disable mipmaps for BGE? Is there a way to reliably disable mipmapping in the file itself, so that blenderplayer will respect the setting and not interpolate textures?

And no, I'm not making a Minecraft clone.
Mipmaps is a system setting, it would be set by the users startup blend file. Not sure that anyone would recommend overriding a users choice.

To change it you would use python to set bpy.context.user_preferences.system.use_mipmaps