Hoarding carts was not a fun thing to do, might be for you as the one stealing. But I can assure you no one likes not having a cart when they want to go farm.People attack castles all the time, especially when there aren’t many defenders/clan members on. Ever heard of a pub war? They happen almost every day. Few people declare war, more and more join over time until small skirmishes turn into an all-out siege. Fun for all involved. Btw, I don’t know who exactly you are referring to as “the majority of the community”, because 80-90% of players are either in clans, about to join one, or part of a family tag group, all of which are totally fine with such chicanery.
You'd be crippling the enjoyment of one of the main aspects of the game by just stealing all the carts and prohibiting any meaningful gameplay / grind since carts are basically the driving force of the economy. It isn't fun.
Seeing as hundreds of people have enjoyed how PW has gone, after all these years are still playing (late last year on NA, even now on EU) and want to come back when the Bannerlord version comes out, I think the way PW is played isn’t the problem. Reinventing the wheel isn’t necessary.
PW offered a unique concept to warband, but that doesn't mean you have to keep within your limitations of the warband engine. People played and enjoyed it because it was fun, but also because they understood the limitations of warband. You'd not be able to get this kind of module to be popular if you'd do it on a game engine like unity and only have all of what warband had, considering the complexity and wide tools you have on unity.
This isn't about reinventing the wheel, it's about making gameplay less of a 20 mins walk to look for a cart and more of 10 mins of creating a cart which is a lot more enjoyable and less tiresome.
A 1:1 copy of PW might work for the first few years, but it won't take long before a competitor pops up with better features, the way PK was to PW and why people switched.