The idea behind the focus points is sound - I rather like that you can concentrate on which skill levels faster than others.
The idea that each level of skill is more expensive in terms of XP is fair. It is not linear. You can learn stuff quickly, but mastering takes years of practice, this feels right.
However, a connection between your level - which should only somewhat represent your "power" or overall experience should NEVER cripple XP gain otherwise it takes away the reason for having foci and makes non-focussed skills unbearable slow.
The learning cap should not be a hard cap, but just reduce the XP gained. This fels right because you can achieve something with enough dilligence even if you are not cut for it otherwise. It just takes (much) longer - but never it should prevent you from trying.
Last thing: the governor skills are a joke because our character cannot use them and I have found, that the charm tree has a perk choice between two governor only skills - seriously? So we have a jump of 50 levels of skill XP until we get something useful again? You, the player should be able to fulfill each job an NPC could do. And even IF you appoint a governor, you can help him with synergy effects - a bit like the field marshal/general system HoI 4 has. The general directly buffs his units with full bonus, but the field marshal does this for all generals under him just adding a fraction of what they get from the general. Like giving 25% of the skill's worth to all governors, if your main character has it. You are the ruling lord after all, the master of the merchant enterprise, the commander of the mercenary band..whatever you are playing, so it should somewhat influence your subordinates.
I do agree with everything you mentioned, but I have to add something for the non-linear exp requirements and how it's not implemented properly in my opinion.
Yes, each level of skill should be more expensive in terms of exp, naturally, but I would argue that the way TW does it is not really sensible. The exp amounts required grow inconsistently, or by a very poor formula. You start with barely 30 exp required let's say for the very first skill, then by 40 skill you are already over 1,200 required exp which is a 40x increase of exp requirement in a very short time-frame. It's not a consistent growth of requirement, that is what seems really bad to me. If skills 1-100 needed let's say each between 1000-3000 exp , and then from skills 100-200 every skill needed between 3000-6000 each, and then from 200-300 = 6000-9000 exp, then that would make more sense. It would be at least resembling a consistent progression, the player would know what to expect. It's just an example, and with this you can set exp gain low enough that leveling up won't be too quick, but it will be consistent which is my biggest gripe with the system to begin with. The way they increase exp required from point A to point B by 100 times more exp needed (because you do need over 30,000 exp at one point for one measly skill point, which is ridiculous) is the biggest flaw of the system. Literally anything will be better than what they currently have made.
What happens in the game is that the requirements go insane at one point and keep increasing inconsistently for no reason at all, it must be a really dumb formula they used and they said: eh, good enough. By getting to over 30,000 exp required for a single skill point, and while leveling speed not only does not stay the same, but it even GOES DOWN, this inconsistency in exp required and exp gained is exactly what causes the first 80 skill points to level INCREDIBLY FAST, and what causes every skill point after to level incredibly slow (=inconsistently bad progression). The problem is not that the system is not linear (because it really shouldn't be), the problem are the numbers, which make leveling up feel downright unsatisfying since you level too quickly at the beginning (=0 sense of accomplishment), and you're praying for level-ups later-on (again, unsatisfying since it's so slow).
So basically, what they can do is:
1) lower exp required amounts per total, and make it more consistent from 1 to 300,
2) adjust exp gained amounts, and don't reduce the learning rate because of level. Can get fewer level-ups so that we don't get too many focus points/attributes etc, that would be fine also. The options are limitless.
3) I do agree with what you say, I said the same thing about the leveling cap. It should be reduced, but never be a hard cap. I would rather start with 0.5 learning rate in every skill (since we start with 2 attribute points), and every attribute give 0.25 learning to every skill (capping to 2.5x learning rate at 10 attributes). And every focus point give 0.5x learning rate and so make it cap at 2.5x, making it a total of 5x learning if you really focus on a skill. Again, this is just an example of how simple it can be and still be better than what it is currently. All the numbers I have mentioned until now can be adjusted at will. The biggest thing to take from this is that the gameplay would benefit greatly with more consistency in progression, lower numbers so that the grind is not as insane as it is now (can make it 1000 to 5000, 5000 to 10000, and 10000 to 15000 too, literally, as long as we don't reach over 20-30-40-50k per skill point I'm happy at this point). And make attributes and focus points give PERMANENT bonuses to learning rate, and lower the learning rate in general so that you don't have to lower it through artificial level-up reducing method.