If you had an impervious barrier between them, you might be able to pull it off. That would at least keep the moisture away from the ice plant. But at issue here is the total environment, not just the soil. Sundew like sun, but their roots cool. Ice plants demand sun and warm, dry soil. While Hen & chicks are not quite so picky, I still don't think it's a good idea.

What you could do with success is plant your Hen & chicks and ice plant on top of rocks or in a depression in a rock where the rock sits on top of the sundew medium. In effect, the two environments would be completely separate, and therefore doable.

As for the soil mix being essentially the same, I suppose it is also doable, but in my opinion, I don't agree. That is, if you are grow alpine type plants. Water retentive soils that copious amounts of peat produce are not good for alpines, especially in humid environments. They naturally grow in mineral soils with low water retention, and low humidity. Just as many alpines die in the summer heat and humidity, as from cold winters. While some alpines are adaptable (like Hens & chicks), others are not.