I wouldn't mind if ME: Next was modeled like DAI. Just so long as it has the one feature that to me represents the core of the Mass Effect franchise: complete and utter emotional annihilation.
Come on devs, bring on the heartbreak! I'm ready to get wrecked. Give me some hard choices (no easy way out!), some cool new guns, and maybe the option to buy a sweatshirt with your rad new logo on it, and I'll be happy.
I'd rather they leave out some of the more mindless fetch quests and just make more story quests. I'm not against some repeatable, optional grind missions though. I'd love for them to bring in the crafting from DAI, that stuff was awesome.
Also, let us keep playing after the end (if it's applicable).
And I agree about the emotional annihilation part. (Incoming DAI spoilers)
I feel Bioware played it soooo safe with DAI. No important people died, Skyhold was never at threat, your actions didn't really effect the ending (though the slides we got were nicer than ME3's original ending), and the last boss/ending kind of just happened. Corypheus just showed up at my doorstep, we fought, game ended. We need more build up. If Mass Effect did anything right, it was building up our victory (and whether or not we got one is debatable).