Before I answer that, I need to digress (again) and describe how real-world multi-language studies work, using the example of Canada, where such studies are common.
(Those who have worked in French in Canada can skip to the next post.)
Nearly 80% of real-world qualitative studies in Montreal are, in my experience, conducted in French by out-of-province clients as part of a larger national or multi-national project, typically originating in and operating in English.
Moderators in Montreal are bilingual in French and English and adapt the English guide to French (often on the fly). To accommodate the client observers and, often, the lead English moderator, facilities in Montreal make provisions for simultaneous interpretation, typically involving a separate studio with audio-hookup to the recording system and the sound system in the observation rooms. The photo shows the setup at MBA Recherches (mentioned here before) and is reproduced with thanks to them and Julie Mayer).

The interpreters themselves are a group of some two dozen reasonably priced freelancers.
They could be a big part of the appeal of qualvu in Canada. More in the next post.