Hopes and wishes for Fire Emblem Switch?
-2D Animation (Sprites are fine but i'd personally love to see a handdrawn entry in the series, if only to see how stylish they could make the transition from map to battle. Also so critical animations aren't so visually dull as they've been in Awakening in Fates, albeit the latter showed some signs of improvement)
-A story and set of villains that isn't/aren't terrible this time (preferably with Yasumi Matsuno scripting it)
-No more <Avatar name here>
-Don't repeat the Soleil debacle/give us gay characters/same sex options if marriages are included (as in more than one and without the creepy conversion therapy)
-If included, handle marriages a la Seisen No Keifu i.e. split the children and (most of) the adults into separate parts of a connected story
-Base conversations to make a comeback
-Keep the My Castle feature from Fates
-If monsters are to be included, have multiple kinds and make them more than simple palette swaps of basic classes
Basically, build off of Fates' excellent structure and correct its relatively easy errors in the next iteration and we could have the best game in the series.