There’s no special way to type accents. You can put them on dedicated keys in a different view. You can have as many views as you want, so you will never run out of space. Make sure that there are enough buttons with the action “change view” and that they make sense.
Long press is in plans, but not the top priority.
The language can be switched from settings. The “preferences” button will open a dedicated switcher in the near future.
Did you check whether there are fallbacks? I have to admit I haven’t tested that.