Fcitx will support spell checker based word hint, and automatically keyboard layout switch.
1. You can use keyboard layout as a single input method, and use corresponding language spell checker.
2. Input method can gives a hint about what keyboard layout it requires, for instance, pinyin will request us layout and fcitx-keyboard can then switch to us layout once pinyin is used.
You can take a look at the code at: https://github.com/fcitx/fcitx-keyboard