To the question of unethical use, we are not talking of stealing somebody's money, this experiment is a part of something more bigger then just money)))
And what's the goal of this "experiment" ?
It could be to see if anyone has researched ways to weaken or break the cryptography of the encryption algorithms that would make cracking the wallets easier than brute forcing each wallet.
That would be horrible experiment because it has ethical concern and uncontrollable parameter. If someone wants to perform such experiment, they should able to control the parameter (such as which software used to generate the wallet and password characteristic) to achieve good result.
I agree with you regarding the ethics of trying to crack these wallets, but there are a lot of researchers who are willing to brush ethics aside for their own personal profit. Just look at all the university professors who are willing to accept money from the Chinese government in secret.
Ignoring the ethics factor, I disagree this would be a bad experiment. It would measure the ability to crack a password intended to secure xx dollars.