In regards to certain criticisms of the BRCS 3.0/3.5 skill system:
The skill system was a good idea but it suffered in one respect of implementation: Too much emphasis on skills.
I.e. 5 ranks of a skill gave you a +1 synergy bonus, with no cap.
This is compounded by the fact that even when taking into account cross-class penalties, certain classes ended up having much more skill points. Particularly when comparing the extremes of say the Fighter vs Rogue.
Furthermore, the addition of 3 skills that had some overlap between other skills and/or abilities.
This could have been scaled down slightly to simply be 5 ranks = standard +2 synergy bonus. Now you might argue “But Phil, then what is the point of having more than 5 ranks?” Well for starters, the Master X feats all require 9 skill ranks; furthermore random event as well as battle resolution is based around a skill check + character (in)actions. Thus the emphasis turns from “you need lots of skill points to be competent as a ruler” to “you need lots of skill points to be an exemplary ruler”
Another way to make it more accessible to certain classes is to modify the war checks like the Feint ability. I.E. include Base Attack bonus to the roll to favor the more martial classes (Fighter, Paladin, Ranger, Barbarian primarily, cleric, druid, rogue, bard secondarily, sorceror and wizard at bottom). This is something that was suggested in the Complete Warrior book where Sense Motive skill was the “strategy skill”.
A good deal of the description of the “lead” skill falls under Diplomacy but also the leadership Feat. You could always include the leadership modifier to such checks if necessary. Rogues tend to not want to necessarily publicize their deeds and the classes based around feats (fighter, lesser extent wizard or classes that gain bonus feats during class progression like ranger) are then mechanically more pre-disposed to take the leadership feat. Particularly as the scion class/template grants a bonus to the leadership score and most of anuire’s strong bloodlines are in the hands of more martial like rulers.
Thus, characters wouldn’t feel quite as compelled to necessarily multiclass as deeply to maximize their potential rulership related skills. Of course, there is nothing stopping a player to take Noble class or rogue levels and so forth to maximize their rulership. But how is that different from a player that twinks out their character to be a melee beast?
As for the debate between how to proceed with domain level play in 4th edition, let’s look back at how 2e functioned as our “base” mechanics.
-RP gain was based on class.
-Specialized proficiencies were in the old “NWP” class groups to limit “cross-class” NWPs.
-Class based bonus abilities towards rulership (free espionage, agitate, etc)
Now, some of the NWPs in 2e were incredibly powerful. Intrigue for example was essentially a free pro-active espionage action with little cost.
So, analyzing this demonstrates that what truly differentiated a Fighter and a Fighter-regent was that the latter controlled a domain and was more likely, albeit it not necessarily, to possess 1 or more NWPs related to maximizing their rulership potential, and a bloodline.
That being said, I think the ideal situation would be to have a scion template that adds specific rulership skills to the (non) player character, in addition to access to the bloodline abilities. Furthermore, the template may give blood abilities or access to blood abilities the character can pick each time they gain a level (say at level 1 you pick animal affinity (minor), and at level 6 you decide to take animal affinity (major) instead of the abilities listed in the PHB for your class). Abilities would scale based on your level just like racial abilities.
Additionally the same could be done for special domain actions. However, we would have to add an additional class of ability (instead of at will, encounter, daily) that would be “domain” and that you gain abilities every few levels accordingly, even if they are just +1 to a roll.
One of the arguments I saw earlier was in regards to the BRCS being made skill based to better port to other campaign settings. Now, I’m not sure what are the limits of WotC “licensing” of the Birthright game to the community, but you have to come to a decision: Either make it a BIRTHRIGHT game mechanic and focus on expanding the SETTING, or make a generic game mechanic system, and use the setting as an example of implementation. Personally, I think the former is a much more interesting use of time.