Actually, the planks are there to keep an eye on the ride height. If a plank gets worn down too much over the course of a race, it means that the ride height has been set too low and the car is illegal (but I don't think there has been a disqualification because of it). Some tolerance is allowed for the car naturally bottoming out - we know this happens; it was what Lotus' reactive ride height system was intended to combat - but it can only go so far. The idea of a spark plate simply changes the component to metal.
Also, I'm surprised that you claim it will lead to another Senna-like accident. You're smarter than that. Yes, the ride height was an issue, but low tyre pressures and damaged steering have also been put forward as causes. The crash itself wasn't that bad; Senna's injuries came about as a result of a suspension upright penetrating his helmet...
It wasn't my smartest answer but, reconsidering my point, I'm going to have another go at explaining it
It seems that the most likely cause of the initial stage of the departure was the car bottoming out on tyres that hadn't reached operating pressure after the safety car period.
The plank was indeed brought in to
keep an eye on ride heights after the accidents that weekend. Low tyre pressures or low suspension settings would be the very advantages that the plank guards against... not to nullify such an advantage but to keep the driver safe.
I can't get past the idea that deliberately introducing parts of the car to the road (for cool effect or otherwise) leads to the risk of a similar departure being initiated, tracks are for the most part much safer than they were in 1994 but there are still corners where such a departure could not be recovered.
The plank isn't supposed to hit the road remember, the penalty is applied when the plank is worn too much after the race. Changing that component to metal... I can't see that
that's a good thing, wood absorbs and wears, metal doesn't, at least not to the "safe" extent of the wooden plank.
I know this is another topic really... but I agree with Williams (specifically Newey) that the initial cause was bottom-out oversteer, without that initial departure we wouldn't be talking about the other appalling elements of Senna's crash.