There is no justification to call them "de France" or "de Navarra". It's Capet and Jimena. That was quite a ridiculous choice to rename them, but that's not a real problem since it's easy to fix by messing in the txt files.
The most and incredibly game breaking addition is to put the same COA for different families. The real "De Navarra" have the same COA as the Jimena. Crovan have the same one as the old Ua Imair. Provence same as Toulouse. Also renaming "de Bouillon" to "de Boulogne" or "de Poitou" to "de Poitiers" is dubious at best. If it wasn't enough confusing some randomly generated nobles gets the same dynastic name as other existing (or already dead) houses. After playing 150 years the game gets way too confusing, this badly needs a fix!!! !!!
Well I'm gonna respond point by point
There is no justification to call them "de France" or "de Navarra". It's Capet and Jimena.
The name Capet has never been the name of the dynasty. No individual other than Hugues Capet ever used that nickname (yes it's a nickname, not even a rare one at that time). As for Jimena it's bad grammar, there are genders in most latin languages and you can't ignore them when borrowing from them. Having people named Alfonso Jimena or Philippe Capétienne sounds utterly ridiculous and ahistorical. You could at best call them house of the capetians and of Ximeno but the capetians are a (very) large dynastic group and how are you gonna justify having all the cadet branches use the regular french naming patterns and not the main line ? If the argument is that it's the academic form then I'm just gonna point that it's the case for all the cadet branches and pretty much all the french dynasties. You would have to rename all of them to Robertiens, Humbertiens, Rodolphiens, Guillelmides, some of these would have dozens of occurences.
The most and incredibly game breaking addition is to put the same COA for different families.
I'm sorry to say but that's what medieval heraldry is. There are very few unique design and a multitude of fairly common ones. Rampant lions for example account for 10 to 20% of all medieval arms (almost twice before 1200) and since there are few possible combinations of colours (only four are common) it's only logical that many families used the same designs. Heraldic groups (the repetitive use of a design and its elements in a political or dynastic group of individuals or lineages) will make this even more obvious.
The real "De Navarra" have the same COA as the Jimena.
That's the same family.
Crovan have the same one as the old Ua Imair.
Should people in dynastic groups living before the birth of heraldry let have random designs or be recreated as heraldic groups ? That's a choice to make and I chose the second possibly. Since you can't prevent old dynasties to use heraldry (would be nasty to have all these people being lowborn, including Charlemagne !) we may aswell have something plausible. That's my opinion at least.
Provence same as Toulouse.
The counts of Toulouse borrowed their arms from the bosonid dynasty. The dynastic conflict over the marquisate of Provence lead all the people involved to wear the same arms : the counts of Provence/Forcalquier (several seals still exist), the counts of Toulouse (several seals too), the former counts of Valence (the Adhémar family, before they split in several branches), the lords of Arles (the Baux family for the cadet branch claiming the viscounty of Marseille), the viscounts of Marseille (the Trets and Fos families), the former counts of Venasque. Even the city of Pisa chose to use the bosonid cross to represent the former marquisate of Tuscany (Pisa was its capital).
Also renaming "de Bouillon" to "de Boulogne" or "de Poitou" to "de Poitiers" is dubious at best
I dont think Godefroy has his own dynasty in the game, does he ? If he has his own (I would argue he should not) it's a simple mistake otherwise he's the son of the count of Boulogne.
As for Poitou and Poitiers it's the proper form in french (it's the same with Genevois and Genève, there's no count of Genevois but a count of Genève).
EDIT : I just checked there's only a Boullion (mispelled) dynasty in vanilla that no character used. I've renamed it to Bouillon (correct spelling) as there was one dynasty of castellans (not really worthy of being included but still I didn't remove the entry). I'm not sure where you got this dubious renaming I'm supposed to have done here.
If it wasn't enough confusing some randomly generated nobles gets the same dynastic name as other existing (or already dead) houses. After playing 150 years the game gets way too confusing, this badly needs a fix!!! !!!
We can't control randomly generated dynasties. They use a cultural pattern and pick a random holding. We've added thousands of historical dynasties but the game only picks them for specific tasks or through events and there's no way to force the game to draw new dynasties from the predefined list. Unless you want us to rename/remove every holding that already has a dynasty named after it, I really don't see what we can do. Even then I don't see a point in making random dynasties stand out, in my opinion everyone should blend together so you don't see behind the curtain too obviously.