I like the idea (because im "gung ho!" realism) but I think once again, you'd have to balance the importance of prestige over something like a shard. I mean a shard is going to give you mana, and allow you to cast spells of its element. To me, this is far more important than a hundred prestige points but that may just be me. However, if prestige gives lots of other bonuses it may be seen as a worthy trade-off.
I'd rather see a system where those things are all tied to that one princess. But in order for this to work we would also have to have noble families. All those possessions would be owned by the house and through their loyalty, you. Let me explain:
You, the sovereign, gets married, lets call you Merlin, Deity of Altar
Merlin is married to Theria but has no children as of yet
meanwhile, in your kingdom you have 3 cities. Camelot, Banbury, and Bromswell
Camelot is the capitol and thus where you and your family reside.
Banbury and Bromswell would be led by a noble family loyal to you, we'll call them uhh... House Yngalur and House Brom respectively
The members of these houses would have children as well, and their daughters would be able to be married off as well.
So for the sake of discussion let's say House Brom has a daughter, you would be able to pick whom she marries as her king.
Now heres where it gets interesting:
If you marry her off to House Aachen in another nation, let's say the Empire of Kraxis, it would boost relations and trade with Kraxis and possibly your prestige in Bromswell if they are stronger, but then Kraxis would have a claim on that city (which would include its people, income, resources, shards, and maybe even armies if units have a "home" like back in the old Civilization days) if her lord father were to die without a son or heir.
Thus it would be like a dowry, but instead of giving it right when the marriage occurs, it would come in the form of a claim. I think it might be easier done this way but again that may just be me.
I'd like to hear what you think