The new rank have the same power as Satraps and this mean that they can set the tax level and set up build queue. This means that Basileus can't ask Chancellor to build there something if the local governor have set up different build queue. They can't however ask recruitment of any units (I leave that power to Basileus and Satraps only) though they can use the garrison to defend the settlement and use them against brigands without asking.
Also, you need only one management point to get this rank and you must be present in the province of that settlement that you govern. This is different from the Satraps who can leave from their Satrapies and still control it.
This should make things more interesting in my opinion. Also, this should bring people who can't lead any of those armies closer to the game if they can at least govern a settlement.