When using the manual focus magnification feature on the A7R2 (and predumably on the other Sony cameras as well), the entire area of the viewfinder or rear LCD screen will fully enlarge to the half or full magnification level, effectively blacking out the field of view to the photographer by filling it with a small portion of the subject.
Rather than fill the area of the viewfidner with just a small portion of the subject, leave the full field of view of the lens to take up the majority of the viewfinder, and superimpose a small box in the center of the screen (or movable by the user) that contains a 100% magnification. This will allow one to observe a scene, aim the camera to put an important part of the subject in the 100% magnification square, focus, recompose, and shoot, all while never taking the photographer's eye off of the field of view. This is how SLRs worked for decades, and also how Lecia's range finder cameras have worked for decades (minus the magnification factor, of course). The reason is, this works! For the photographer, the field of view is paramount! A focus aid should not disconnect the photographer from the scene.
Here is a link to a petition to show Sony that this request is supported. Please sign it!
youtube Link to see video of problem & solution: