1. The metabones adapter has that tripod mount thing that makes it difficult to fit in a housing, unless housing manufacturers make an allowance for it.
2. Even if it goes down to f0.7, nobody is going to shoot at the f stop because of the hyperfocal (eg. 20mm) is about 20m? The metabones is great for terrestrial filmmakers, but the application won't solve the problems of noise, even on the S35 4k (if and when it comes out!)
1. The metabones tripod mount is removable.
2a Not sure what you're saying with that first sentence, but as you are effectively using more area of the lens to project a image on the sensor you might also conclude that you have more light hitting the sensor for any given f stop. Now this might produce a very shallow depth of field wide open, but that was never my point?
2b Not sure where this fits into a discussion about the pocket camera, but I would argue that you would get better low light capability with the 4K sensor than the 2.5K sensor all else being equal. i.e you resample 4K down to HD, which I think the majority of shooters are thinking. Now there is probably a penalty on the sensor due to global shutter with the 4k version so they (vs 2.5K EF mount) might come out around the same, but surely a BMCC MFT with a speed booster would give you more light.
Correct me if I'm wrong but do have a look at the New (made for Black magic MFT cameras) speed boosters released on monday.