A Compact camera makes a good companion

Over time, I've been wondering what format of camera I should get, or in other words, what size of sensor I should purchase for a camera; and my choices have ranged all of the way from tiny 1/4" inch sensors (Difficult to find), past 1" sensors, Micro 4/3 sensors, all of the way to FF. My conclusion, at least so far, is that a compact camera with a relatively small sensor makes a good companion to a Full Frame SLR, but of course, not everyone can afford FF, so I'd say that my hypothesis, if you're an enthusiast or amateur photographer, is to go for a premium compact, and if you can then save up for a full frame camera; I think it should be worth it! But why would an FF camera go well with a compact? Well, one of the reasons that I can think of is image quality vs portability; If you want the image quality to be optimal at one hundred percent magnification, then go for FF, and if you also need something to be very portable, then go for a compact camera. The FF camera can give you much shallower depth of field, especially if the lens specs of both cameras are identical. As I've already mentioned in an earlier post, for macro photography, a small sensor can in many instances compare or even exceed the image quality of a full frame camera, at least when it comes down to DOF. However, there's also another benefit of using a compact camera for macro; It is easier for a smaller sensor to obtain higher magnification. And for landscapes, portraits, and maybe sports as well, you will probably prefer the image quality that comes out of an FF camera. On an FF camera, however, an f/stop that's lower than about f/1.0 or so is obtainable, as opposed to a compact sensor camera. Perhaps if you use a camera with a sensor in-between an FF and a compact camera's sensor, such as micro 4/3, then with enough experience and/or technical know how, you can achieve both the results of an FF as well as that of a compact camera. However, to my best knowledge and experience, I'd most likely like to rather have both a compact as well as a compact camera; that or some camera manufacturer should come out with an interchangeable sensor camera? I don't think that it would work too well however, because lenses to match what the sensors see would have to be designed differently. If you have an FF camera, then you can have the compact camera in your pocket and take it out and perhaps more quickly take a photo as opposed to the FF camera. And here's comes another benefit to owning multiple cameras. Settings and menus on cameras can be really quite daunting to learn. So, if you have one camera set to one setting, and the other camera's set to another setting, then you'll increase the chances of getting the perfect photo. Also, you can, for instance, have a 10mm wide angle lens on your compact camera, while having a telephoto prime on the FF camera; therefore, you don't need an extra lens for the FF camera. Personally, I enjoy it when my compact camera has a very wide lens (but not fisheye) and if the quickest aperture is relatively slow such as f/5, because then the sweet spot, or the optimal aperture at which the photo can be produced with the most detail, will be relatively slow, meaning that I can take photos with a potentially impressive amount of DOF without; as I go past ever slower apertures on the camera's aperture setting, it will take me a higher f/stop to reach in order to introduce any diffraction, unlike a compact camera lens which is great for lowlight performance, where the sweet spot is a number at which depth of field isn't quite as high as in the example that I just offered. And if I have such a compact camera, with a slow lens, then a FF camera with a quick lens is the way to go in my opinion, to add as a companion. If only they, camera manufacturers, made a compact camera with ISO values as low as 1, then long exposures could be more easy; or at least if they had stronger ND filters built in, that would be really nice to add to the market. Light painting using macro, for example, could become a much more creative process, due to technical considerations. And it'd be nice also to add a built in Polarizing filter to cameras; no more filters that you could possibly lose! And furthermore, theoretically at least, it'd save time if you could just press a button or dial and have a filter be implemented, as opposed to having to screw in an external filter; plus, the internal filters could be made cheaper than external filters because they'd be much smaller; Okay, now I do regret to some extent not getting (upgrading to) a different camera.