No offense (I don't know your skill set) but if the devs/programmers around here have already done that and no one has found a solution, why try? If you are REALLY that curious than I would like to inform you that the "MCU" brick is tantamount of a hardware brick, which as stated requires a replacement.
Why the hell would you want to brick yourself on purpose when not one person has successfully recovered from one? I'd also like to mention that if you visit 3D Brew you will see that the MCU SoC buses (there are two) control a hell of a lot more than just the LED lights which was the big deal with closing the lid on a N3DS in 2.1... The MCU also controls the volume slider, the camera, the LCD screens, the Home button and a lot more.
I have seen at least two "perm" bricks that were related to the MCU and a broken camera ribbon cable. Of course he didn't assume it was hardware since the screen would init from the bootrom, but not the homemenu but after BOTH of them opened the chassis and repaired the cable it worked fine.
I don't see how you plan to fix a system module that is stuck in a circle of reading bad data, failing, and attempting to read it again on a loop. You would need to stop it to even get into the console. I mean honestly you may be able to disable the LED light altogether from the motherboard and fix it that way, but no one has tried since I'm pretty sure that would require damaging the MCU SoC (I'm not sure if there is a tiny cable from the MCU to the LED). If you do that, you're breaking more than you're fixing and you're going to end up with a crap system anyway.
Makes you wonder why everyone says they can't even be fixed with a hardmod; that implies you can't fix it without breaking other necessary components for the console to run; or that it's impossible TO fix.