Depends if you’re talking about 1500lm at 20C ambient without breeze or outside at 10C with breeze, and at which regulated temperature.
In this Zebralight SC700D review Zebralight SC700d – A Short Technical Review (lumens/runtime graphs/temperature/PWM/current draw)
It does 900lm inside, 2000lm inside with fan, and ~1700 outside at 7C ambient with wind gusts.
The SC700D uses an XHP70.2 5000K 90CRI driven by an efficient boost converter in a light body so that’s pretty impressive already, a low CRI LED would do even better.
I wonder how well a D4Sv2 (with boost driver) with low CRI cool white LH351Ds would do (most efficient 3535 3V LED), XHP35.2s would do a bit better, and with a 5050 MCPCB, XHP50.3s, I’m thinking it would be pretty close to the 1500lm target at room temp.
As for copper, it’s not really useful except for adding weight and increasing a bit turbo duration thanks to its ~1.4 volumetric heat capacity vs aluminium, but that doesn’t matter for sustained output.