Was playing EU4 with the M&T mod. First thing I noticed was that with their autonomy system, I had to mod the tax penalty out as the AI simply didn't know how to play with the tax penalty. Upon removing it, the AI began behaving cleverly again (by EU4 standards).
After doing some Knights of Rhodes runs just to calibrate stuff, started off as England. Unlike in normal EU4, the communication times between London and France before you can start building roads everywhere causes severe autonomy issues, thus in order to maximize resources for the war effort all available lands were turned over to Aquitaine or Gascogne for administration. The English won the first few battles, staving off the French and carving a few chunks of France away into Aquitaine, however Paris was not taken. I was waiting for the crucial moment when the English would be able to field longbowmen, as that would rapidly shift the quality of armed forces away from the men at arms of France to the longbowmen of England. All the while this occurred I sought allies but found none, which was an issue as France found suitable allies in both Aragon and Castile, rendering them impervious to English initiated wars even at their weakest. Unable to do much but conquer some independent counts in the France region, England turned its attention towards integrating Scotland and Ireland into a British-isles superstate, anticipating that this would improve chances at securing the French throne (especially as it removed Scotland from the French coalition and added its troops to the English cause).
The next war went incredibly well, the longbowmen inflicting immense casualties on the French. There was just one issue; the English did not have enough resources to afford
victory, especially as the Castilians were hammering the English alongside the French, and the Royal Navy was not of such a size that it could take both countries on at the same time. To avoid having to surrender with a Franco-Spanish invasion of Wessex and London, vassalage of Gascogne and some gold was forked over. As the French had lost some land and were hurting manpower wise, they accepted this peace. Gascogne was eventually attacked and its lands incorporated into Aquitaine, all the while the English navy expanded in size and scope, the Scottish and English nations growing closer and Ireland being assimilated by diplomacy, alliance and warfare. Things would go especially well once I secured an alliance with Portugal, Sweden and Naples - with Portugal and Naples providing very powerful counterbalances to the Mediterranean Iberian powers, whilst Sweden kept Norway pacified.
I was rather worried however, in the geographical difficulties faced by my predicament. Portugal and Naples were a fitting counterbalance, however my Aquitaine didn't have strategic depth; I could not surprise attack the French as their Fortresses were behind the hills and mountains surrounding Aquitaine, hill forts and mountains I needed to control to solidify Aquitaine's security as a sure thing. Without a secure Aquitaine, I simply would never be able to keep an army encamped around Paris long enough (as Castile and France would always be able to link up Forces in the time it would take to siege Paris), meaning France would ultimately be victorious.
Things would go horribly wrong when I declared war again, facing much the same problem again. It was simply far easier for the French to siege Aquitaine than it was for the English to siege their hillforts, and so the English were forced to abandon all their Norman cores & their gains in Aquitaine from the first successful quarter. I regathered my forces, amassing a large navy and army, building roads throughout Britain wherever possible and waited for the right time to strike France. The moment arrived when France got drawn into a Castilian-Aragonese war which bled it dry, after which it was struck by a plague. With the French King depleted of manpower and his provinces devastated by plague, that left only the French nobles and Aragon to contend with. The attack which could have secured Aquitaine or even Paris itself was about to commence, when the French gained control of the curia. My King was excommunicated by the Pope, forcing Naples to abandon their alliance with England. The French declared war with the aid of Burgundy and Aragon, my faith in the longbowmen was well-founded, but the superior resources of France was simply an insurmountable thing to beat.
This would mark the extent of England's French ambitions. Notice Aquitaine's geographical boundaries of mountains and rivers are all held by French or French allied nobles. I never lost faith in the superior combat ability of the longbowmen even after that, but after more failed wars, I had to contend with the fact that ultimate victory was impossible - I should have just tried sieging Paris generations ago. High chance of failure, yes, but it was the only chance of victory.
I realized then that I had fallen into the exact same overconfidence and beliefs as did the monarchs of the hundred years war and felt rather foolish, for repeating their mistakes and doing things like dying. This would lay the foundations of the future Anglo nation however - as the monarchy sold Calais and began departing from Aquitaine (looting it for all the gold it had before giving the immensely angry nobles independence). Looting Aquitaine and granting it independence was the only wise move I made in the whole hundred years war.
Defending it was impossible, but by granting it independence it caused a war between Castile and France over which power would hold sway, causing both enemies of England to attack each other. In the aftermath of the war Castile lost Galicia, which promptly got diplomatically protected by Portugal, and Aquitaine lost pretty much all of her lands that wasn't protected by mountain forts.
Aquitaine became a city-state with 1 port and 1 fort, a vital English naval base from which to strike Castile and France, that England held on to for far longer than seemed possible. Excommunication in M&T is also far more brutal, lost all stability, got hit by a plague, isolated England diplomatically, killed any possible hope for a reconquest and permanently damaged Anglo-Papal relations. When the French set up their own anti-pope, England supported the Roman pope, then decided to forgo popes altogether and embrace the Calixtine heresy causing 3 generations of religious warfare (that turned into 4 when one King turned out to be a closet Catholic).
My one happy moment was getting revenge on Sweden for betraying our alliance - they got invaded by a Danish-Norwegian alliance. England wrecked Norway and Denmark, and as a result left the war having annexed Iceland. This still left Sweden on her own, and thus Sweden got partitioned between Denmark and Norway anyways. Interestingly, Silesians and England taking the Calixtine heresy seems to have slowed down the reformation considerably