Does MultiSig wallet may include functions like increaseSupply, decreaseSupply and functionality like blackList addresses?
MultiSig Wallets are actually smart contracts that are meant to replace your normal accounts and add multiple signers that can "create" and "approve" transactions before they are actually executed.
They can include functionality like "black lists".
Most implementations are able to call any method on any contract, so yes, your multisig could be the owner of a "token contract" and it can be used to call increaseSupply() / mint() / transfer().
Their only limitation i can think of, is that they cannot be used for "personal message signing" ( See details about eth_sign ), as there is no "private key" to be used for such a case, so it cannot really be used for cases like "authentication".
Let me know if that answers your questions.