With all characters from Playstation, Xbox and Nintendo + release on all consoles with crossplay.

Could this become the best selling and most enjoyable game of all time? This would bring the console war to a whole new level with gamers representing their platforms. lol

Don't worry, it won't be long until this is possible on the Switch. We're already moving in that direction anyway.

Well that would mean less fire emblem chars

Even more boring characters that I don't even know? No thanks.

Serious question: How did Playstation AllStars Battle Royale turnout? Did they capture the Smash magic? Were there great characters, and how was the roster in general?

Really doubt that we will see Kratos, Nathan Drake or Master Chief for Smash in the near future.

"PlayStation All-Stars Battle Royale has received reviews that ranged from average to generally favorable. Critics praised the game's multiplayer and fighting mechanics, but criticized its lack of content, still images in campaign mode and few cut scenes. The use of super moves as the only way to defeat a player had mixed reception. While some critics thought it lacked depth, others believed that filling up the meter to land a knock-out added strategy to an otherwise only decent fighting experience. The game currently holds a 74 score for the PlayStation 3 version and a 75 score for the PS Vita version on Metacritic."

Source: https://en.wikipedia.org/wiki/PlayStation_All-Stars_Battle_Royale

Haha...I'm sure you're right...but the concept you're referring to seems a tad more far fetched, no?  And I wouldn't count anything out at this point with the positive relationships Nintendo and Sakurai seem to be cultivating.  There's no denying that Nintendo is having the biggest gaming party of all time over on the Switch with Smash Bros and I understand why all the cool kids from the other consoles want to come see what it looks like from the inside.  I can't fault you for that. But thinking you could just move that party wherever you want and repeat the magic seems a bit optimistic.  And as much of a stretch that it seems that Nathan Drake, Kratos, and Master Chief would come over to Nintendo's house for a fun romp, I think it's even less likely Nintendo will let Mario go galavanting around in another fighting game on another system.  Some random turn based tactical fighter, sure...but a Smash clone.  Not a chance.

Would harm smash sales and probably Nintendo hardware sales. I'd love destroying Masterchief and Spiderman with Duck Hunt, don't get me wrong, but I just don't see it happening.

They tried too hard to be "not Smash Bros." and the mechanics suffered. There is no damage. Basic attacks only build up a special meter, and only these special attacks can kill opponents. It's not too bad in a 4 player brawl, but once you are down to 2 people it becomes very tedious.