Victoria 2 was rather famous for it's tedious rebellion system and also for it's rather static warfare system in general, especially in how it completely failed to represent the massive shifts in warfare that happened in the game's lategame. I've seen so many discussions over the years online on how war should be handled in an (at that time) hypothetical Victoria 3, people had a lot of ideas on how it could transition from a system more akin to the traditional paradox GSG war system to something more akin to the frontlines of heart of iron, but none of those were as radical as the changes that the dev diary seems to suggest.
Though it's all pretty vague right now, and we'll have to wait and see how they'll actually implement it, I'm very excited about some of the things that dev diary contained. It looks like it could potentially be the most realistic implementation of war in a pdx gsg yet. I love the boldness of removing units that you move yourself, if I'm controlling a government I shouldn't be micromanaging exactly where each regiment goes marching, that should be left to my general staff! It's one of those things where less player control seems like it could be more immersive, something that I've also dreamt about for a lot of other pdx games.
In general I'm just excited to see any change as radical as this to a pdx gsg, they do kind of feel like the same game in a different outfit at times, I hope they'll dare to do moves as bold as this when/if they do EU5 in the future. But I'll try to calm my hype, we still don't know how the final product will look like.
This does seem to make provinces less and less relevant though, I for one am looking forward to the day when we get a PDX game that shed provinces entirely and give us a totally free-range map where borders, towns, army placement etc can be truly dynamic.