Scans describing the story and systems are starting to appear, can't link them but in one of them you can see Validar from Fire Emblem Awakening (non-playable apparently but might be a boss or something).
EDIT : thanks to Blackkite here :
https://twitter.com/bk2128/status/905108444889268224
- Class Change confirmed, also by using Master Seal item. Shion/Rowan (& Lianna) can promote from Lord to Master Lord.
- will have Skill system. Can equip up to 3 skills. Skills are unlocked by bonding with other characters.
- has Emblem Shop system, apparently involving using materials & permanent stat boosts... need better scan to scrutinize
- History Mode is separate from Story Mode. It retells the original story of each FE game featured.
- In History Mode you'd move charas on 2D grids like the original SRPG. When ally adjacent to enemy, battle will trigger
- Famitsu shows that Validar will appear but as enemy NPC. Scenes in History Mode will also be fully voiced.
- And Famitsu notes that this History Mode map is from Shadow Dragon. Hope we can get better look at tomorrow's HQ scans
History mode sounds like the equivalent of Adventure mode in Hyrule Warriors, but with an actual story.