TBH, I believe that you'd run into problems with too high light density before the problems with cooling (I'm talking about CXB3590). If we can agree that an average of 1500 umol/s/m^2 is the goal, there will never be a need for you to remove more than about 320W/m^2 (3590 @50% efficiency) -- an amount well manageable with conventional HS.
My idea of perfect design is close to what SDS does or what most most commercial LED lights - an enclosed, plug&play, maintenance-free unit. Kind of the opposite of what you're making. Therefore my answer would be no. This answer might be a little biased, though.
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This argument will go away, eventually. LEDs are improving - hitting 70% efficiency now - and soon they'll produce almost no heat. Ie if today's 70% LEDs are improved to 80%, the output will improve by 14% while the heat will be reduced by 33%.