J, looking at their description... could you not use a relay (or micro-relay) to take the PWM input of the signal bulb (BL/GN wire on headlight harness) and then output clean +12v to the LED driver's white wire (low power 50% brightness)?

Then take the positive wire from the sidemarker lights to trigger the yellow (signal) input for your halos.

The red (high 100% brightness) could be connected to any +12v acc and ground to any ground.

I included a diagram of the headlight but I didn't know (or more likely, remember) what year your X was. This is a LCI 2005 w/ xenon & ALC.

Wired as I describe above... I believe you will achieve 100% during daylight hours. 50% as soon as you activate parking lights (either by auto selection or manual). And amber signal as soon as the turn signal is activated.

Attached Images

 

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)