2 crucial things CKII skips

[PANGI]

As feudal monarch you probably spent most of your time dealing with your vassals yet 2 most important things you had to negotiate are not modeled in the game - war machine and loans.

Current war machinery is pretty much conscript system like from the second half of 17 century onward - when you have some percentage of men whose are obligated to be at your service at war and theyre ready to go right after you call. Medieval monarchs didnt have this luxury and except men from own fiefs and mercenaries they had to negotiate with their vassals how many men they will provide and it was up to vassals judgement and mood.

and as a vassal you have pretty much 3 options:
- send everything you can and personally participate because you expect some gains from the campaign - like looting profit and titles of conquered territories or other favors from you liege. also if you are personally motivated in the goals your dedication is naturally stronger
- your not interested and send only some symbolical force to not offend your liege
- your relations with your lord are not good and you naturally wont obey but expect his hate

Secure your vassals support was the most important thing every monarch had to do before every campaign - now its pretty much non existing. And yet this would help with issue that youre not really motivated to give someone a title - to make him stronger, because he could be only a threat to you. But with this system if you know hes your strong supporter you give him titles because you know in future campaign you will have more men for war (yeah at some degree this is present in game regarding factions but you know...)

As for loans - now you as well hit magical button and money are there from no one knows where. Sounds like bank loan - but banks are distant future also. If monarch wanted a money he had to borrow them mostly from his vassals and they naturally wanted something in return - like titles or privileges.
Somewhat related to this topic is also elective monarchy mechanics - HRE specifically. No emperor was elected without bribing - this was pretty much obligatory.

...my 2 cents

 

[Humanoid Typhoon]

A good way to think about it is that the feudal realm laws is your agreement with your vassals on how much levy they should provide you. As for loans and bribes, I don't think loans should be represented in-game at all besides what is in now (Borrowing from the Jews or Holy Orders). Adding more things would mean demesne income and vassal taxes would need to be nerfed and opinion rebalanced and it would just get to a point where everything is a major cluster fudge for new players. Bribes however are represented in-game and have been around since before I started playing CK2.

If you are looking for any of these things maybe you could try some of the large gameplay conversion mods? (CK2+, When the World Stopped Making Sense, HIP or Lux Invicta)

If I misinterpreted what you meant I apologize, this is just my opinion.

 

[PANGI]

Well realm laws are pretty much conscription system in the end. You have same amount of troops from every province for every war you start. But this amount should vary from vassal to vassal and from war to war depending on vassals interest in it and your relations...
for example:
defending against infidels - pretty much all available men from realm
pressing some vassal claim - strong support from that vassal
pressing my claim - vassals not very interested unless promised something etc.

Also now you have no option to send nothing to your liege and there are situation when this should be the case - like most powerful duke with his own mind.
HRE is such superpower just becouse emperor can gather soldiers from every province but in reality this practically never happened.

I know loans as proposed would shake current economy, but borrowing from your vassals was omnipresent (jews and holy orders were exceptions) and many kings lost a lot of their power just because they need money and now this didnt exist at all and yet it is such crucial aspect of vassal-liege relations. Kings had lot of debts which was great opportunity for rich vassals.

 

[Shebaloso]

As feudal monarch you probably spent most of your time dealing with your vassals yet 2 most important things you had to negotiate are not modeled in the game - war machine and loans.

Current war machinery is pretty much conscript system like from the second half of 17 century onward - when you have some percentage of men whose are obligated to be at your service at war and theyre ready to go right after you call. Medieval monarchs didnt have this luxury and except men from own fiefs and mercenaries they had to negotiate with their vassals how many men they will provide and it was up to vassals judgement and mood.

and as a vassal you have pretty much 3 options:
- send everything you can and personally participate because you expect some gains from the campaign - like looting profit and titles of conquered territories or other favors from you liege. also if you are personally motivated in the goals your dedication is naturally stronger
- your not interested and send only some symbolical force to not offend your liege
- your relations with your lord are not good and you naturally wont obey but expect his hate

Secure your vassals support was the most important thing every monarch had to do before every campaign - now its pretty much non existing. And yet this would help with issue that youre not really motivated to give someone a title - to make him stronger, because he could be only a threat to you. But with this system if you know hes your strong supporter you give him titles because you know in future campaign you will have more men for war (yeah at some degree this is present in game regarding factions but you know...)

As for loans - now you as well hit magical button and money are there from no one knows where. Sounds like bank loan - but banks are distant future also. If monarch wanted a money he had to borrow them mostly from his vassals and they naturally wanted something in return - like titles or privileges.
Somewhat related to this topic is also elective monarchy mechanics - HRE specifically. No emperor was elected without bribing - this was pretty much obligatory.

...my 2 cents

Let us remember that the vassal was OBLIGATED by law to send troops to his liege, just like his liege was OBLIGATED by law to protect his vassal. Not fulfilling the suzerainty/vassalage agreement was legal basis for hostile action. That said, i think your points are already represented in the game:

1. You already have some benefits if you are a commander fighting for your liege. You gain prestige from the position, prestige from battles, a monthly pay and i believe some of the loot after a siege and military points ( i maybe wrong here though). As a commander, there are also events that prompt you to offer military education for you liege's other commanders, which, if accepted, grant you a favor which then can be used in a variety of ways, including making him declare wars outside his realm for YOUR claims. On the other hand, merely sending the required levy to your liege should not provide any benefit AT ALL, as all that your liege is required to do by the feudal system is to protect your lands in case of aggression

2. Already represented in the game. A loyal vassal would have a large opinion and provide more levies (proportional to his opinion) than one with a low opinion. But the vassal with the low opinion is indeed required to provide a minimum levy, which is defined by your realm laws.

3. Securing your vassal's support before a large war is STILL very important, specially if you rule a large realm composed by dozens of duchies. Sure, it certainly became easier with conclave, as your councillors cannot join factions while the council is content (if the war declaration comitee still exists), but if your vassal's opinions suddenly start going below 0 during the war, you are certainly in for a rough ride. Money will stop flowing, levies will be at minimum and factions will form.

4. The money comes from the jews in the realm, not a banking institution. Likewise, vassals can offer donations to their lords in exchange for favors, in case the lord accepts, and the build war chest ambition allows you to get money by force from your subjects. Besides, there are some events that allows you to ask your friends for money and others in which they offer monetary help by themselves. And there are still the holy orders, which may lend you money but then can make demands on you, such as demanding your sons to join them, asking for land, etc.

5. There is bribing in the game, and it's pretty much mandatory in an elective government unless your heir is a grey eminence and you are a demi god with all the positive traits