If there any kind of illegal activities involved in that transaction then if there is bitcoin bank exist over there then some kind of transactions may be stop by the bank.
Sounds like a joke. Bitcoin is a decentralized coin. If it becomes centralized then what is the point? you mean to say the coin should loss its unique property?
Owning a bitcoin probably need the private key required to access your bitcoin in a secure wallet. Now, if there is a bank of bitcoin, do you think your private key is safe anymore? That's the difference of a centralized and decentralized cryptocurrency. Don't trust any banks be your own bank.