I understand your point of view but I am trying to understand why is so, because I cannot find anything RAW that clearly points in that direction.
According to my reading, in the section MODEL PROFILES, it is pretty clear that the models are the ones that get the rules (subsection "Special rules") and when they join together the unit applies the rules from the models (so the "unit" itself does not have any special rule). This is implied in the section "Unit size" and in the way is written
Characters & Formations.
On the other hand, reviewing how is written "Master of Battle" special rule implies that units and character are different entities and units can also get rules. Or it is just a shortcut for "all other models in the unit".
Master of Battle: If this model joins a unit of Empire Knights, Inner Circle Knights or Demigryph Knights, that unit will gain the Immune to Psychology special rule. Should this model leave a unit it has joined for any reason, that unit loses this special rule.So, IMHO when we are adding more models to a unit, they add their rules to the unit (when we are creating the army list, they are actually copies of the same special rules except for characters). That's why we also get some special rules written "all models in the unit" or "majority of models in the unit".
IMHO and I guess RAW a unit
has a rule when any of the models
has the rule. Therefore, a model with Frenzy, Hatred (X), Immune to Psychology or Stubborn joining a regimental unit with dettachments should confer
those special rules onto its detachments whilst they are within 3" of itAlso RAW, although the Witch Hunter's Immune to Psychology is not extended to the other regimental unit's models, when we check the "majority of the models" condition is not fullfilled and the unit ignores "
automatically passes any Fear, Panic or Terror tests" and also can
flee as a charge reaction. However the unit still has the special rule.
So, in one scenario, if a character is a separate entity when joins a unit (as implied by
Master of Battle), then we can only provide the magic items (and the sweet additional special rules) to a champion or standard bearer to add the rules to the Regimental Units and then extend it to the dettachments using the Dettachment special rules.
In the other scenario, if a character becomes part of the unit when joins it, his special rules are added to the unit special rules (although they may not be applicable because of the "majority of the models" restrictions).
I also checked the FAQ (
https://www.warhammer-community.com/wp-content/uploads/2024/01/ScGm8K4WG9pa9sGv.pdf ) and the change to the weapon only says:
P
age 339 – Berserker Blade
Add the following note to the weapon profile:
‘Notes: The wielder of the Berserker Blade is Frenzied.So it still gets the Frenzy rule.