After looking at a number of more recent long beam flashlights (using HPX 70.2, 50.2) I came back to this from the above thread:
Trustfire 3T6 Detachable 3800LM Flashlight Integrated
Replacement LED Bulb 3 CREE XM-L2
for $19 on Amazon as the most reasonable solution (cost, weight, light) and ordered one to test, in spite of it being "old technology".
Here are some of my notes after looking at https://www.stratusleds.com/module
Easy to get carried away. One could use solenoid or servo controlled inlets in the wing LE ducted to the LED or its heat sink.
Their 140lumens/watt started me looking. Cree apparently achieved 303lm/W in the lab -- but a long way from the 135lm/W in the XHP 70.2. Theoretical limit for a white LED with phosphorescence color mixing is something like 260-300lm/W (40% efficiency).
Interestingly, comparing XM-L2 (10W) to CXA3590 (150W):
Maximum Efficacy at Binning Conditions: 175 lm/W
Maximum Efficacy at Binning Conditions: 150 lm/W
the XM-L2 is more efficient.
("Binning" is the manufacturer's sorting produced LED into bins of different efficiencies, colors, etc. Looks like binning conditions are about half the power the LEDs are rated for and LEDs can be over driven to deliver more light at cost of more power and more heat to be gotten rid of.)
At $19 a pop, it's easy to mount, easy to double or triple or ...
and you get lens, reflector, LED and heat sink all in one.
If anyone has corrections to the above numbers, please do post them here.