I've tested a few tools in this area, and I think the biggest issue with real-time face changing isn't really the face itself — it's keeping the result believable while the person is moving. Things like lighting, head rotation, fast movement and especially mouth/eye movement can make the effect obvious pretty quickly. For content production, I'd rather use face changing selectively for short shots than try to keep a synthetic face on someone for an entire video. Shorter shots also make it much easier to hide imperfections during editing. If you're making ads or social content, you can cut around the weak frames and keep the effect looking much more natural.