Certainly these extensions are possible in future versions of MultiChain, based on user demand.
In the meantime you also have the option of granting certain privileges to multisignature addresses (e.g. 2-of-3). This allows consensus to be required for the corresponding operations from specific addresses by having a transaction signed by multiple parties.
It doesn't work exactly like administrator consensus, because the transaction needs to be passed between the parties (either off-chain or on-chain using streams) to reach the level of consensus, rather than the consensus being built by MultiChain based on individual signed transactions. But it might work for you nonetheless.
For more information: http://www.multichain.com/developers/multisignature-transactions/