errr im going with... its probably possible but it might not look so great.
Presumably youd equip it in you helmet slot i guess? Im fairly sure you can have a helmet (or any other item) that uses all of the bones in the skeleton, which, if done properly would allow it to move, seemingly on top of the armour.
There would likely be a fair bit of awkward stretching - cloaks look much better on games that use gravity and collision to allow the cloaks to "drop" onto the armour. Here you'd be stretching it with the bone animation which would look unnatural. For me this is the biggest turn-off.
An additional obstacle is the wide range of armour shapes available. If you placed the cloak such that it avoided collision with all armours including massive armour shoulder plates, it would sit way off the shoulders and hang most unnaturally if you didnt have massive armour equipped.
It might be possible with scripting to check for the "shape" of the armour and have several cloak models which better match a given shape. when the player changes equipment, the cloak could be destroyed and replaced by one with a more suitable model.
The best way to avoid the problems above are to have more of a "cowl and cape" than "full cloak". Tie the hood at the front to the body/armour in a way that explains its lack of movement, and avoid having it over too much of the shoulder so that the arms would not ordinarily move it. a short cape would explain the lack of movement as the player ran. Imagine Ezio from Assassin's Creed, except without the flowing cape. It kinda loses something...
I would suggest experimentation before you put too much time into modelling and rigging the model to the bones.