See Crypt Ransacker.

Very comparable to Infernal Tutor, though I'm not sure if that means this should cost one more.

No, this is much weaker. I even considered making it a cantrip.

No, a 1 mana tutor seems pretty bonkers to me

It is bonkers; but there's some others. They tend to have "If you can't find the card you want quickly, you lose" kinds of downsides though.

But this is just "You don't cast it until you really need to" which isn't a very big downside at all.

But this costs an extra card! Not only that, but one of your opponent's choice!

A card that won't win the game versus a card that will. That's not much of a cost. Gamble is totally playable, and sometimes you discard the card you tutored for!

It probably helps to think of it not as your opponent getting to thoughtseize you, and more as "Trade the best card in your hand for the best card in your library."

Gee look at the Roar of the Wurm, Fiery Temper, Anger or Bridge From Below you are making me discard this turn. Whatever shall I do! ;)

Indeed. You do have to not be hellbent, which is a minor hoop to jump through. But it's certainly one that can be twisted to an advantage.

It does mean you can't search for the second half of a combo when you have the first in hand. But only if the first needs to be in hand, if it's on the battlefield, then getting the second half is probably worth any other card.

This could probably cost 1BB and still be good, although I do think that you should be able to tutor even if you have no card to discard. It's a small upside, but it's the kind of puzzle that should be rewarded