I'm envisioning a tiny shield which contains an array of buck/boost converters for driving high-power LEDs (1-5 watt, 2.8/3.8 Vf).  Something that can maybe even be jumpered or regulated to accept different voltages in (3.3, 5, 6, 9, 12), can handle 350mA per line, and control fading with PWM.

this definitely gets my vote.