That is, unless you, like you said, somehow manually combined them, which would be a b**** to do and likely not yield great results.
Hm, it's not that hard. Especially with the new editor. All you need is a separate track for each language, and when the notes overlap you just put the same notes on the other tracks (with a similar vowel transition to the one you want), and then silence the notes you don't want played with dynamics.
The biggest problem is making sure all the banks have the same tone as each other, and even that's not something to worry about unless there's a HUGE difference in tone between them.