Yes, i would love an Yandere/ Walking Fan type character, the latter being pretty unexplored in Modern FE, while we already got Tharja Camilla Faye. Though as an guy that's obssesed with the trope i would certainly love it to comeback.
Every 3ds game got a Yandere, meybe not 3H but it's up for debate with like 1 or 2 people, 3 Hopes had Monica though. So im actually pretty sad and sulking no Yan got announced yet.
Yandere not being here would be fine aside from my crying lol, though ironically enough i think it makes the most sense for Alear and not someone like Corrin to get one. I never seen a Fan trope, would love to see how IS would work it out!
I miss Beast units too, they've added Wolf Riders! not the same... also Bears are cool so,
The idea with the Masked character seems super cool. Never seen one but your ( Mordred's!) description sounds sick :}