It's not just fair and unethical, but also against the rules. At least, playing with/against yourself to gain ELO with it, is against the rules.
And entering the same tournament, means you can also be matched against your alternate self.
There is - in my eyes - nothing wrong with having a duplicate account, you may have a good reason for it. I have an alt account, named...'Voriki alt', and I played 2 training games against myself, nothing ELO increasing.
But abusing the free right to create multiple accounts is in my eyes, very bad.
Since what you propose is already not allowed, you just have to report the profiles and provide proof, I see no reason why people should upvote your suggestion. The admins are already aware.
But, I may have a different proposition.
We could "legalize" multi-accounts, but you have to report them yourselves. I suggest to expand the friend feature where you can indicate different levels of friendship, only visible to the admins.
You can indicate one friend, who is your sibling, living at the same address, same IP. Or you can indicate it is an alt you have access to to the account.
Then the system will not allow you to enter tables at the same time where you may gain ELO.
Since there is a legalization procedure, it makes it more justified if someone does not report their own multiaccounts, or other users playing at the same IP, and the admins can take appropriate actions.