Pardon me, my electrical engineering know-how is next to nothing.

I meant, couldn't we add a resistor post LED to create the same effect?

Edit: love the safety hat orange too OP!

__________________
-Typos courtesy of my mobile phone.

FOund this on a different car forum, Not a merc, but looks like it might be a solution... The wiring colors are incorrect so dont go by them.

"
Start with the "normal" warning lamp configuration where a white wire goes from the ignition switch, to the lamp, out the lamp via a brown/yellow wire and finally off to the alternator. Replace the warning lamp with a 40 Ohm power resistor (something rated for at least 1 Watt). NOW get your LED lamp assembly. A plain LED will need a "dropping resistor", typically 1000 Ohms. A pre-configured LED warning lamp will already have this resistor inside. Take your LED lamp (or LED with dropping resistor) and wire it in PARALLEL with the 40 Ohm power resistor. Pay attention to the polarity or the LED will not light. With the LED wired in parallel to the 40 Watt resistor... the LED will turn on and off just like a normal incandescent light. However, the current required to power the alternator field coils on startup will pass through the 40 Watt resistor."

Anyways, I'm attempting this myself, I'll report if I have any luck.