What you're describing is called "Forced Subtitles". I think there's an option in makemkv to always include forced subtitles, but I'm not sure. Either way, it doesn't always work and still won't include the forced subtitles. On those blurays where it doesn't work, in Makemkv you can include all English subtitles into the mkv file. Then figure out which one is the one that only translates foreign languages by cycling through the subtitle tracks. Then use MKVMerge to mark that subtitle track as the Forced one. There are also ways to 'burn' a subtitle track onto the movie itself with Handbrake but i've never done that.