Come on, Minecraft does not pretend the implement classical physics.
The problem isn't lack of rigour, is that it gives you the wrong intuition. For example, the essential feature that distinguishes superposition from a classical mixture is that there is a basis in which the result of a measurement is deterministic, and from what I have seen this is not the case in the mod.
One way that it could be done: a "superposition" block, that can be prepared in the states |0>, |1>, |+>, or |->. If you look at it vertically, you measure in the Z basis, and if you continue measuring in the Z basis, the result doesn't change. If you then measure in the X basis, it's gonna collapse randomly to either |+> or |->, and it's gonna keep being this one as long as you keep looking at it vertically.
And this gives you also complementarity, which I think is one of the fundamental quantum concepts. The way the "observation" block was implemented simply makes no sense whatsoever. It's just a block that is different depending on the way you look. There is no complementarity between the aspects of the block, or anything to deal with the randomness of the quantum observation.
I don't understand what are you talking about teleportation. It doesn't sound to me very much related to real quantum teleportation. But I think the trouble with teleportation is that it is actually quite boring, and would serve no purpose in a game.
But it would be nice if we had some "quantum interaction" thingie (a CNOT) that would take two "superpositions" in different basis to an entangled state, and with this entangled state we could run the chsh game or ek91 qcrypto protocol.