I don't think it would be a good idea. Map input is a lot more flexible, and also this is not as often used feature. For some of the light source shapes it doesn't even make any sense. So since it's not as frequently used, and since this solution would be only for very specific thing, it would just clutter the UI. If you need this advanced effect, you definitely should go the extra mile of using gradient with CoronaColor plugged in.
From my experience, sooner or later, everyone wants to push themselves a bit further, in this case, one would probably start to use real photographed HDR images of lighting apertures to push realism even further, and the checkbox would remain forgotten, just creating visual clutter.
Map input already allows for this, and much more, so it really would not make sense to have two ways of doing same thing, one more flexible, other one less flexible.
