How was it overall? I never really got chance to play it back in the day, but all the new QOL additions seem great.
I already played it back in the day so I was just trying to get to the new stuff. It's really cleaned up, like its amazing how all it took was some minor changes. New UI I'm a bit iffy on since I liked having character level progress visible at all times while grinding, and you don't get the duplicate TP and HP bar on the arts tray anymore, so doing overdrive makes you have to look up to the party and back, which is annoying.
Other than that all, the actual gameplay changes are extremely minor like adding a new quick art button that lets you skip art charge at the cost of energy, and the bar only refills outside of combat, so it really speeds the combat up a lot, no more downtime, you unlock it for Skells too after you complete the new ending. They removed BLADE levels entirely, so you can open any field treasure or FN site without needing to grind or come back later (outside a couple that needed field skill 5 in the original, which I guess the quest still exists), and the field treasure isn't button mash anymore, just hold A. New UI lets you access everything from anywhere now, although you still need to return to the barracks to get your Skell back if it dies. Quest tracker is copied from Xenoblade 3 essentially, and now it tracks world collectables for you which is nice. Lastly level cap is uncapped to 99, no longer 60, but the game is still balanced around level 60 cap, so EXP scaling reflects that, and the new final boss is level 60.
They added 4 new party members with new Arts and storylines;
NielNail, the Qlurian archeologist, the Skell test pilot who I was convinced would be a they/them given Treehouse's track record but she isn't, Ga Jiarg, and Al the lone hero from the intro and the main character of the new chapters. Essentially all the new stuff was in the Japanese artbook in the unused/classified materials section, so its extremely likely they've had this all planned from the start but ran into development troubles and or hardware limitations on the Wii U.
New music is really good, better than a lot of the original tracks, they got Sawano back for it, alongside a new composer, Misaki Umase. Sawano did some arrangements of old tracks, and to me it sounds like once you reach the new chapters its entirely Umase's stuff, and its really good, very Xenosaga-esque in a lot of ways.
Overall it's really good, X was always my favorite so my bias is shining through, but its honestly the best playing game Monolith has made in my opinion, and the new story harkens back to Xenosaga along with a lot of big lore drops, although they are done via exposition and animatics, presumably budget related and them needing the story told for the sequel, which I'm 99% sure is whats happening next. Don't rush to chapter 13 after finishing chapter 12 (the original ending), play the rest of the game first, its very much an epilogue meant for when you are all done, and it locks you out of the rest of the game until you finish it, where it then throws you back to after chapter 12 on a postgame save.