I'd also like to keep the whole marriage and matchmaker aspect that we saw in awakening and fates out unless they figure out how to tastefully weave it into the storyline.
I think Genealogy of the Holy War best (and first) implemented the kids thing. There's a time skip, and your party in the second part of the game is composed of the kids of the first party (if they paired up) and new characters, too. I could gush on about FE4 when I have more time lol.
I'm thinking akin to how the Total War series handles army battles but making the choices of how to play each battle as being either classic turn-based tactical mode or going full musou hack'n'slash nonsense as options for gameplay.
My memory is hazy, but I think Divinity: Dragon Commander had something like this? A turn based strategy map, RTS battles, and you can activate your commander as a hero unit you directly control.