So some thoughts on what we might be seeing soon:
Cheers Luv, the Cavalry Mages are here. Take Nino, Tharja and Odin's tomes away, and give them to Cecilia, Leo and Olwen/Reinhardt. You now have 3 mounted mages with full color coverage, who can all get buffed by Hone Cavalry (Atk/Spd +6) and Fortify Cavalry (Def/Res +6). That means they can all travel 3 spaces and drop a fat nuke of +24 damage on anyone not explicitly tailored to beat mages. Oh, and give them all Moonbow for shits and giggles, inflicting Def/Res -30% every 3 actions (increased from the default 2), and no amount of Resilience will save you.
Archers more OP than in Fate/stay night. They can all have Gordin/Klein's Brave Bow+ now. Skills may include Close Counter, Death Blow, Vantage, Tomebreakers, Quick Riposte, Savage Blow, and whatever specials tickle your fancy. Fliers will likely be able to inherit Michalis's Svalinn Shield to get rid of the bow weakness, but will it really matter when archers can one shot them without it?
The "I can survive a nuclear apocalypse" club. In what's looking to become a one-shot meta, the few characters who can take a hit and survive it could become the counter meta. Quite literally, since you can stick Counters on them all and let your opponents kill themselves on your team. Special shout out to Effie; You thought she hit hard before, wait until you see her with Brave Lance+, a Special to proc, and Hone Armor buffs. The only thing harder than deciding between Death Blow 3 and Distant Counter will be Effie's herculean musculature.
The "Coldsteel the Hedgeheg" Defense Meta. Just when you thought you were safe, it turns out the entire enemy team was equipped with Wings of Mercy, Escape Route, Lunge, Drag Back, Smite and Pivot. *Olivia casually tosses Effie over a mountain.* *Lucina Teleports behind you* "psssh... nothin personnel... kid..."
Dragons are Eternal. All the Dragons can now inherit Nowi and Adult Tiki's Lightning Breath+ and Corrin(F)'s Dark Breath+. Is there any reason to use Adult Tiki when Young Tiki can steal her weapon and has higher BST? Not to mention, Dragons are already tanky enough to survive all but the fattest of nukes. Now you can equip them with more practical specials, give them all Assist skills, give them Fortify Dragons (Def/Res +6) or Threaten skills for C, Vantage or Quick Riposte for B, and Death Blow or Fury for A. As is proper for a team of dragons, however, achieving this will take a mountain of gold, considering the number of Ninians and Tikis you would want to roll. This is an endeavor for whales with more sophisticated tastes.
May the Gods have mercy on our souls.