focal length compatibility shouldnt be of concern here. the front optic looks to be way large enough to accommodate as wide taking lens as the cinelux or similar will allow. this fm module wont add any additional vignette. so full frame users will be able to shoot 3.55:1 ratio on an 85mm with little to no vignette, aps-c a 50mm, and m4/3 a 35mm.
I think there is far too much thinking with regard to how important having multiple focal lengths actually is within the film making process. The importance becomes even less so when you're shooting anamorphic on a big sensor and resolutions to allow cropping. imo just find the widest taking lens and leave it there. then crop in or move closer for tighter shots:) an 85mm + 2x anamorphot and a full frame sensor cropped at the edges to 4:3 is really wide. the same on aps-c with a 50mm, and the same on m4/3 with a 35mm.