TL;DR  That is scary!

That looks too good to be true.
The reward would be huge; but if it bricks the device, the loss will be huge.
I would only try if I were absolutely comfortable bricking the device.
Even if the software were audited and proven to work perfectly in theory, the hardware is the "in practice" side of the equation. For example, in theory a switch or push button is a simple "true or false" read; in practice, it needs a debouncer and possibly calibration.

A malicious firmware could make the chips run at full power and turn the fans off, thus burning all hashing boards.
At that point, whether it can brick the control board too is relatively irrelevant if all hashboard melted.

A non malicious firmware could do the same because of some bug or by being installed on the wrong target device.

Bitcoin ASICs are probably the most optimized chips ever created. I can't think of any chip with as much incentive for optimization. Yet, some obscure "asic to the moon" website claims to DOUBLE the output of such chips. That also imply that it doubles the performance because the power supply cannot give double the amount of power, nor do its power cables. And the electrical circuit it is connected to probably can't provide that power either.

I think it is also worth to point out that the more device that are taken offline, the lower the global hashrate; so there is an incentive. And a clever malicious firmware could "run just fine for a couple weeks", just long enough to make someone confident to install the same firmware on all its miners, and then strike the whole farm at once.

I would love, sincerely, to hear counterarguments.