it should be possible to make a better reference cooler. Even one with two fans even if one of the fans only serves to accelerate the air pushed by the first fan. couple heat pipes tucked in there and bam!
Don't know about the 2 fans in a blower style cooler. Where would the put the heatsink in addition to the extra fan? Wouldn't that mean less heatsink for the GPU? Sounds like a zero sum gain to me. Unless you make the card longer or wider, it's going to be pretty hard to displace 250 watts without it being hot and loud.