kind of, the point of this system is that you can leverage the network for escrow transactions so long as everything goes to plan, thereby ensuring a low cost. in instances of dispute, you will pay a third party.
I'd go too with websites offering escrow services. The network is quiet complex as it is, without having to add all the confirmation, delay and dispute stuff.
Currently when a transaction is broadcast it'll sooner or later be added to the block chain, what you are asking for is a mechanism to tentatively add a transaction and then dispute it later.
Also who do you think will be the third party moderating the dispute? There is no real advantage in adding it to the protocol itself.