With Fire Emblem Switch stated for this year, here's my thought. 

With both the shake up on Mario and Zelda being so big that even Game Freak is going 'you know, let's change our formula up more' if the word is correct, could Fire Emblem try something like that? 

I mean you could argue they already did that with Awakening and Fates, (or Sun and Moon for Pokemon) , but could they try something like that? 

Zelda and Mario became a lot more open. I don't see how they'd do that with Fire Emblem.

FE already had a shake up in Awakening.

Just being bigger and better is probably good enough.

HD waifu / husbando and hard but fair, fluid combat is enough to sell the game.

Meh, it doesn't really need it. But it could put a unique spin on the series. I always wanted a FE game where you play as a Pirate crew rather than a traditional army. What I do what for sure however, is the toning down of the weeaboo/waifu pandering that plagued Fates. I didn't mind Awkening's anime tropes since they were done in a clever way. But Fates took it way too far.

I think Awakening/Fates settled the artstyle which is already a BIG for a series that relies so much on its characters, now they should try to flesh out the gameplay, maybe implementing some of the features from Echoes

Many could receive that treatment to be honest.Mario and Luigi RPG could use that setup, like using Odyssey assets and overall artstyle, with a new or at least heavily improved battle system taking advantage of the game being truly 3D for example.Nintendo could bring back Golden Sun and give it another try.I dont think that FE needs it, given that bringing the awakening new ideas and making overall improvements to a home console would be big enough by itself.

Mario, Zelda and Pokemon have always done well, these recent titles only prove that innovation pays off and is what the gaming industry needs. It only did these already higly succesful franchises and Nintendo a huge favor both in reception and sales.

Fire Emblem already had it's shake up with Awakening and it's doing well ever since especially with that mobile game.

Metroid and Star Fox however are in dire need of a BoTW/Oddysey shake up.

I think adventure and platform games have a lot more flexibility than SRPGs, and so there's a lot more room for formula shake-ups in games like Mario and Zelda. Unless you change the genre itself, there likely won't be any shifts as big as Awakening saw, and if the genre itself is changing, I'd personally they rather label it as a spinoff a la Warriors.

Open relationships?