im not sure how it's possible that youre vassals in newly conquered territory can emmediatly raise up full levy's from those territory's, given the normal "new administrtion" modifiers to conquered province's. perhaps it's because either those pirate vassals get troops from specific slave pirate buildings or even slave buildings. A max slave camp for ex will give you quite a lot of men regardless if the lcal castle levy got depleted iirc. And pirate's just like wildlings have specific castle holdings like wildling barracks/pirate den, these also provide men regardless of the actual castle's levy, and perhaps it's so that just like with wildling baracks these holdings can be improved with prestige. As such, what might be happening is that by granted lands to pirate's they gain certain buildings that give them men regardless of the province it's levy.

Martial 10 isn't too hard to get, give me time and i can create a solid line of martial 30 characters. Education is something i can go into a lot of detail, there are many aspects to it, but one of the key things indeed is having first of all acces to good educators. And that doesn't mean that they just need to be good in martial score. How good a kid can get depends on a number of things which can all be maximized.

There is base stats first of all trough genetic traits. A genius gets base 5 martial of the bat, if he's strong too it will be 7 iirc because strong gives +2. hige also gives a positive modifier, so does quick with +3 martial. Maximizing the production of epic stat characters requires lots of breeding of people with quality genetic traits, which can be done the more so over time. Besides that you can make good rulers, brilliant people tend to be also better educators for ex. because their stats are more all round.

A very important and overlooked factor is learning, the more learnign a kid aquires during his education, the faster he can build up his stats trough learnign from a character. A kid with 10 learning will learn more martial points from a 17 martial educator than a kid with 5 learning. A specific kid will also probably learn more martial points from a martial with 17 martial skill and 12 learning skill than from a marchal with 21 marchal skill and 3 learning. You want to have optimal learning on educator and student. if needed you can give a kid with very poor learning to a maester with very high learning for the first 5 years of his education just so that he aquire's some basic learning to later assig to a more specefic educator which can teach him a speciality.

Learnign modifying raits. And the consideration that as youre main character is the best at giving kids specific traits. A kid that can get learning improving traits like dilligent, ambitious, patient and a few more will get learn far more trough their education from their eucators than those who have negative traits for that regard liek say slothfull or arbitrary. Kids that are given to educators can get fairly random traits even if the traits of the educator matter somewhat. When youre the educator yourself it's easier to use the events to get mostly positive outcome's so you want youre ruler to educate a lot and for that matter you want youre dude to be a good educator but that usually follows from him being a good educator.

Maester and marchal. maesters have education events towards kids in youre courts, and you want to get rid of bad maesters for it sucks when they give kids negative modifiers randomly. You want maesters with high learnign and fairly ositive traits around all the time. Marchals can also be ordered to train kids in fighting and usually that is what my marhel be doing and he will be carefully sellected for that task too. there is more information in the tooltip if you hover over the train children button for the marchal that gives you likelyhoods of good or bad training. You could either have overall positive effects or overall negative effects, but it isn't too hard to get something like 12 to 15 out of 20 chance fo a positive event and limit the chance for a negative effect to something like 2%. The highest martial score isn't so determinal here, more important is the swordsmanship skill of the educator and other favourable traits in regards to personallity and education. Certainly if you want to produce a lot of formidable wariors (skill level 4 in swordmanship) then youll need a good formidable warrior as educator and thats often hard to get, so if you can get formidable warriors then you should try to keep making good educators for this trough the gennerations.

As a pirate you might find that it's harder to find a lot of good bride's, simply because the pool of avialable pirate women is a lot smaller. Afaik it can be somewhat alleviated by stealing women, or perhaps it's only ironborn who can do this with their saltwomen. (sure can pay of to abduct targaryans hah) it's not the easiest learnign school for how to create youre perfect character trough education ill grant you that.