DA:I has a good narrative that pulls you through the game, I'd like that again. ME1's 'go to any planet you like first' system is great for choice, but you don't experience the repercussions of your actions as all those planets are essentially in stasis until you get there. Same with DA:O.
In Inquisition your previous actions are referenced in later quests, there's a sense that time has moved on. Also of being a nobody, then building an Inquisition, getting more successful and powerful as time goes on, and earning your stripes by the end.
However let's cut the ludicrous amount of zones, either cutting each by 30% or just losing some altogether.
I personally would like more chunky side quests, like ME3, that have more of a role in the story. It would be great to have 2 crises at once and you're forced to choose. Whichever you chose the other will get worse by the time you get there, and vise versa. That would add replay value.
So I guess I'm asking for the linear storytelling of ME3 and DA:I, with some more freedom added in the side quests.
The companions were great, romances were great, the only thing I'd add is more chances to dislike ppl and for them to dislike you. If I'm a terrible Inquisitor let Cullen and Leliana regret their decision to pick me. Let me dislike Garrus, or Liara, or Anderson, and that dislike lead to a cutscene or extra dialogue. Not just 'I don't like you so I'm leaving the mission, even though the world is ending and I should probably stay and help...'. 
Let me be pro-Cerberus and hate the Alliance for imprisoning me, let me be a bad Inquisitor or a selfish one. I don't want to be railroaded into being Space Jesus again.