i could not disagree with you more!! I think the open world elements in DA:I are a great success and add a fun element of exploration to the game. The localized quests in each open world area could have been better overall. More quests like the missing patrol in Fallowmire or the drowned town in Crestview would have been better over some of the MMO-style fetch quests we got. Over all, though, it added a great new dynamic to the gameplay and a very refreshing change from the small linear environments in DA2. I will give you that the character interactions (NPC to NPC, not NPC to player) took a small step back from DA2 but it was still better than in DA:O where they had almost no interaction with each other outside banter while we explored. I honestly believe that if they do it at least as good as it was done in DA:I that open world type environments could work great in ME:A. Especially if there is the focus on exploration that I am hoping there will be based on what little of the premise has been hinted at. Imagine scouting out large zones on various planets to identify resources to keep your mission going (not like you can zip back to Earth to refuel and resupply any time stock runs low) or trying to identify viable spots for colonization. I think that would be awesome!!!
I actually like the idea of an open world. The trouble is the execution doesn't really work, because it will probably mean a much shorter main story and more linear everything else. DAI is a good example this, because as nicely rendered as those zones were having them caused everything else to suffer and backtrack. Linear and overly short main story, no cutscenes at all in the "zones", poor story zone to main plot story integration, Robot dialogue everywhere, outdated character interaction, character cutscenes happening too quickly, weird and nonsensical issues related to the fact they're running all over Thedas in presumably days what should take weeks/months which distorted the sense of time throughout the story. Probably other stuff I'm forgetting.
If we could get main content at the quality of the original trilogy with decent amount of story relevant missions AND what you described, I'd be thrilled, but I don't think it's realistic at all and probably won't happen. Probably F04 mixed with Destiny more likely, ick.