Echoes is an incredibly close remake to Gaiden. In fact, the biggest criticism against Echoes is that they transferred most of the gameplay from an antiquated NES RPG with few changes. Sure, they drastically expanded the story and added some new mechanics like combat arts, supports, and three exploration for the dungeons, but the core gameplay loop, mechanics, and level design are translated one for one from Gaiden.
New Mystery of the Emblem definitely diverts from Mystery of the Emblem more than Echoes diverts from Gaiden, but it still has the same foundation. The level design is more or less identical and that's not that most of the mechanical changes are minor beyond getting rid of dismounting and adding reclassing.
If you wanted to remake Genealogy in the style of Thracia, you'd need to cut the massive maps, the individual gold pools, weapons being repairable, the distribution of weapons, enemy placement, and the stats of the enemies. If you wanted to remake Thracia in the style of Genealogy, you'd have to cut the capture mechanic, the steal mechanic, the dismount mechanic, and literally every map in the game.
I really want both of these games remade too, but I also want them remade well. What makes Genealogy and Thracia so fun to play 20+ years after their releases are what they do differently from other entries. Likewise, their narratives are designed around their gameplay, so you're harming both the gameplay and the story. I'd much rather see two good remakes over the next 5 years than a good remake and a bad one crammed into one package.