Let me preface this by saying I just started playing FE after not having touched Elemental since the release, so to the extent that something has already been decided, I am probably not aware.  That said I did just read the .90 changelog, so hopefully I'm not beating any dead horses.

Is marriage gone for good? Sad if so - it was a fun mechanic although it did seem very difficult to implement correctly.

I have two balance concerns about spells (apologies if these have already been raised). First, Dirge of Ceresa - this spell seems to be useless against many higher level Independent creatures (who seem to totally resist it or be immune? not 100% sure) but it absolutely mows down other nations armies. I focused my Ceresa on spellcasting and by the mid-game she could pretty much annihilate any stack enemy nations could field in one turn - plus I had that +10 initiative at the start of the battle trait, which meant the casting time was irrelevant, she would cast it immediately. For example, in one cast against an enemy group of roughly 250 hp, she dealt about 2000 damage. The only thing that could survive even one cast was the enemy sovereign. So that seems a little OP and maybe should be nerfed.

The other spell that concerns me is Mana Blast. I recruited a champion reasonably early (lvl 5 I think he was, but he might have been level 3) who had this spell, and shortly afterward I noticed it on my sovereign and other champions (is that gotten through research somewhere?). Anyway, for a base cost of 30 mana, assuming you have decent size reserves, this spell deals obscene damage even if they resist. I started near a fair amount of shards, and for mid game it wasn't difficult to build up reserves of 1500-2000, which means even a resisted cast is dealing 75-100 damage a pop. Makes the bonuses from the shards for all the elemental spells nearly useless. My sovereign and four champions took down a group of 5 Obsidian Golems using this spell exclusively and it wasn't even close. Without this spell I don't think there's any way I could have won.

My other suggestions have to do with flavor, mostly the ending. One minor thing I noticed - at the end when you get a score and a "bio" of someone based on that score, it seems that you even though the bios of the people who correspond to lesser scores are revealed, you can't click on them to read about them, which seems silly.

My bigger flavor gripe was the ending screen - as um, whatever the Wraith empire's name is, I was basically an evil bastard. So it was a little jarring, upon brutally conquering the last rival city with my Death magic and hordes of Wraith-people, to see a picture of a very vanilla, clean, blue skies and sparkling towers city followed by a short speal on how recovery can now begin or whatnot. Didn't really fit at all. So some kind of minor efforts there could probably really improve the flavor feel.

Again, apologies if any of this is wasted effort.