For the question of traditional vs Awakening-style, I'd definitely have to go with traditional. One of the reasons that Awakening was so easy comparatively to the others (on Normal mode, not Lunatic or Lunatic+ mind you, although those don't compare to Radiant Dawn's Japanese Hard Mode seriously that was literally the hardest thing ever) was because of the easy accessibility for grinding. In the traditional games, you had to think much more strategically about where to place your units so they could gain levels, but be at risk or not, which made you think more. Awakening doesn't have that same charm.
However, I absolutely loved the Paralogues in Awakening, so I believe that they should take the Fire Emblem: Rekka No Ken route and do the optional sidequests with certain objectives needing to be completed in order to get them. This would encourage multiple playthroughs.
As for the children characters, I honestly don't really feel the need for children anymore. Like, in Awakening, it was important to the story because of the whole Fell Dragon concept and turning back the clock to set things right again, but I absolutely abhorred how the children characters and the marriage system ended up shafting development of the characters in terms of supports and Barracks conversations.
Like, if they're in, fine, but don't shaft out development or meaningful supports for the parent characters just to get the children.
For the new game, I also want more Victory conditions other than Route the Enemy or Defeat the Boss. The Defend victory option from Radiant Dawn (sorry for referring to this game a lot, it's one of my personal favorites and first Fire Emblem game) was a cool twist, and so did the Enemies That Need to Be Taken Down (killing certain number of enemies, forcing aggression and carefulness into your strategy).
In another subject, what controller ports do you guys use, since port priority is apparently not a thing anymore? I personally use the second player because the blue victory background contrasts better with default Robin's outfit.