I posted a suggestion like this last November, but its been almost a year and still nothing. So here it is again.
Original post:
If you replace a noble with another dwarf, you need to reassign the office and other rooms to the new noble. An prime example would be the Mayor, you can't control who becomes mayor and by this time he should have an office and private dining. When a new mayor gets elected, the old mayor should automatically move out of the mayor's manor and clear out his desk at the office so the new one can move in.
A solution: when [a]ssigning rooms, there should be a sub menu with "Individual [d]warves" and "[n]oble positions", where the later option gives a list of current available positions as seen on the [n]oble/administrators menu.
Addition to original post:
If a Dwarf holds more than one Administrator job, i.e. Broker/Manager, they get two offices/bedrooms/dining rooms or the player can just one as you don't really need to give him another set, the holdings of one position can meet the requirements of the other. But in the instance of multiple holdings, he could pick the best one or just use the nearest one and relish in the fact that he has two houses.
More foreseeable problems:
After the economy kicks in, the old mayor or other appointees will still have his stuff in the rooms and I know how dwarves are so reluctant to pick up after themselves and so they may leave their stuff in other people's rooms and... well that's dwarven capitalism for you.