My problem with that is that those courtiers you appoint as chancellor et. al. represent the minor nobles of in your land come to court to be in the presence of their liege. However, I find it wrong that an improper set up for the higher ranks. The King of France wouldn't necessarily appoint Robert of the Isle, Lord of Backwaterville as the Lord Chancellor of All France, nor would Lord Robert probably be a regular at the King's court. Instead, the King would be surrounded by his closest advisors and the ambitious upper nobility such that the King would be more pressured to appoint Lord William, Duc de Provence as the Lord Chancellor.
It's been a while since I looked at french medieval history, but I think even at the royal level it was members of the lwoer nobility holding the royal offices...
Just quickly looking at a couple of osprey books I find:
Charles de Montmorency as Constable of France (equivalent to the marshal) at Crecy. The de Montmorency were originally of the lesser nobility (they only became dukes in the 16th century, before that they were lords, than barons) from Isle de France. Looking at their wikipedia article I find that 6 marshals, 12 constables and 4 admirals (another office we need) of France were of this family...
Eustace de Ribeaumont was standard bearer at Poitiers, he was just a simple knight (not sure we should include that office in CK-II, though many down to the countly courts had such an office)...
Geoffrey de Chargny was oriflamme bearer at Poitiers (this office I expect should be excluded from CK-II as it's too close to the standard bearer and unique to France)...
John le Meingre (Boucicaut) was marshal of France from 1356 to his death in 1367, he seems to have been a minor knight originally, his son John II would be marshal in turn...
Looking at the list of marshals and constables of France on wikipedia I find that early on the constables were always held by members of the lesser nobility (occasionaly simple knights not even lords), later as they gained prestige and I assume power by members of the upper nobility (counts or even dukes in their own right), the marshals were throughout almost always lesser nobility (near the end of the 15th century exceptions start to appear), the office of chancelor was almost exclusivbely held by members of the clergy roughly half of them bishops (so land owning in CK-II I assume)...
I didn't look at any more offices, but I think I've already disproven the point I originally wanted to make. Originally these royal offices were held by minor (in CK-II terms landless) nobles, later on as the power and prestige of the offices grew more powerful characters sought out such positions. So people ruling land in their own name should be possible to be nominated for offices...