Obviously, any designated MILF lens _could_ include the equivalent of a converter bolted on. Thus, anything that is possible (optically) when you design a DSLR camera + DSLR lens, is also possible when you design a MILF camera + MILF lens. What you gain is the possibility of designing lenses that could never have been used on a DSLR due to the mirror: lenses that include optical elements very close to the sensor.
It is safe to assume that having more freedom to design something is never negative. It seems that in this case, for certain designs, it allows some features that are positive for image quality, compactness etc. But if you take advantage of those features, you also get some drawbacks.
Why is it that film could accept wide angles of incoming light while digital cannot? Is this a fundamental property of ccd/cmos sensors, or is it some trade-off (perhaps with micro-lenses/sensitivity)?