Actually a Fire Emblem Soul Calibur game would be pretty awesome, kinda like what they did with Hyrule Warriors.

Like others said...I would like to see a Fire Emblem vs Xenoblade fighting game done in the vein of Guilty Gear/Persona Arena.

I'd also like Fire Emblem Warriors-esque game that adheres to more of the Fire Emblem strategy, but that's neither here nor there

I´ll like a nintendo vs capcom, but that is unlikely to happen

Who has ever said that.

Excuse me.....a Fire Emblem fighting game. Better?

Streets of Rage.

Capcom v Nintendo if possible.
Pokken - they can really make an iteration of it for NX if it would be a smash hit, which i think it will.
Fire Emblem x Soul Caliber would be nice

would adding Sega x Capcom x Nintendo better? not sure if there are a lot of IPs Sega can add, maybe but don't know if those IPs are exclusive to Sony or so.

Bloody Roar

-Pokken Fighters is an obvious choice. If they release new versions every now and then could be good.
-Revive Power Stone like others have said. Great games with a unique combat system.
-Revive Bloody Roar, I absolutely LOVED the gamecube one. Looked and played amazing. If they could just up the production values would be awesome.
-If Nintendo could nab a lesser title say Soul Calibur and make it successful again would be great.