Let me take a look at it for you. As you said, as long as the other party's house is legally acquired property with the right to use. He can use it freely, including transfer and lease. Because there is no real estate license and land use certificate. Therefore, when a house is registered or put on record, the first person to obtain the right to use it is the person who manages the use of the property. If there is any change, it must be solved by the original owner. Therefore, only the right to use can be transferred, not the property right.

There is also the contract law, as long as it is an agreement reached by both parties through consultation. Moreover, there is an intermediary who has no interest to certify that the signed contract is valid. Both sides must abide by it. If there is a breach of contract, the court will support the contract.

As you said, both parties can sign the contract with Party A directly after canceling the contract. There's no need to go around in a big circle. But if it involves house demolition, it must be legally agreed with Party A. It doesn't matter if you bring others. I don't know if what I said can help you, but you'd better check and confirm some specific relevant laws and regulations! ! ! !