Knoll Light Factory was far more advanced than simply adding 'dumb' flares. As you moved the target point (for the light) around the image it would change the properties of the elements of the flare depending on distance from the centre and angle to the centre-line of the image and would create extra artifacts when positioned close to the image edges. The various elements would also react differently based on background colour. It did it all quickly and easily too, along with the ability to fully customise the elements of each flare and save presets... that's the functionality I want.
I can think of several flare filters, but none with the level of functionality that you want. Flares are so passe' and cliche' now they don't get much attention. I use brushes and just modify the brush once stamped, to my needs, but I do understand where you're coming from.