1) Well, I'll offer an alternative viewpoint. Four characters in a D&D game is too few and is plainly insulting to me coming from a Goldbox background. I certainly wouldn't care if the combat is longer providing if it were sufficiently tweaked to be more dynamic; with more options and more possible party compositions as a result.
To differentiate itself properly from the likes of Dragon Age Origins and Original Sin, I really think it needs the option of six characters to be more in line with Baldurs Gate tradition. Changing the fixed party nonsense after Act I should also be reconsidered to enable greater player choice; also in line with Baldur's Gate tradition.
2) Greater, stronger, more obvious connections to the original games. Whether that be companions, locations, music - I think a greater emphasis on making the game feel like Baldur's Gate is necessary. Admittedly we haven't seen the city yet, so it'lll be very interesting what the act 2 content will be like.
3) Memorable Dungeons. (Durlag's Tower, Watcher's Keep etc) Aye, it's EA, so it's still very early days yet. But this is something BG is well known for and is a vital ingredient for a quality Baldur's Gate experience. Also, what's with encountering the Underdark at such a low level? Doesn't strike me as particularly suitable given its dangers and how it appears in BG2.
4) More companions. Obviously it'll be interesting to see what Larian's take on Minsc will be. Pity we don't get Xan or Edwin too though. I know there's already a big datamining thread on the official forums that has already delved into exactly who the additional companions are.
5) A real-time with pause toggle for the fans of this combat system. The reverse was possible for Obsidian when they implemented a turn based mode for PoE2. I wonder how conceivable this would be for Larian to create? It certainly would help those who don't like the longer drawn out combat encounters.