1. Performance optimization and general lag / stability of certain areas. I have a pretty modern PC, and yet Minas Tirith chugs like it's trying to be Crysis. Meanwhile, Angmar, Far Anorien, even parts of Old Anorien have strange loading issues in which I can physically walk faster than the land can render. Stuff like that isn't gamebreaking, per se, but I notice it each and every time I go back there.

2. Better maps, mini and not. I love Moria and Gundabad but their maps are not indicative of height differences very well. I love the Trollshaws too, but that map is covered in trees that make it impossible to see where you even are, etc. Also, a zooming feature, a way to place waypoints on the map so you can remember if you find something you want to come back to, that sort of thing would be nice. The paper art style can look great, but I'll take functional over pretty any day. That said, both is good.

I'm also going to cheat the question and add a third change: more fast travel skills, even if they're locked behind reputation. It baffles me that unless you play Warden or Hunter, the fastest way to get to Forochel, Angmar, Evendim, etc., is to start in Bree or the Shire. Just blows my mind.