What if there were PSASBR-style crossover stages?

[Perkilator]

Playstation All-Stars Battle Royale is undoubtedly a controversial game for multiple reasons, but one of the more positively received aspects of the game was how its took two franchises and crossed them over (for example, Metal Gear invading Locoroco, Killzone invading Harappa the Rapper, etc.). So what if Smash did the same thing? It can be any two franchises you want from the following companies represented:

• Nintendo
• Konami
• SEGA
• Capcom
• Namco
• Square Enix
• ATLUS
• Microsoft
• SNK
• Disney

Just for some examples, here's a Reddit post I found with some visual aids:
https://www.reddit.com/r/SmashBrosUltimate/comments/nrfq39

 

[Mamboo07]

I can imagine a Mushroom Kingdom stage invaded by Ganon's evil army and monsters from Zelda series

 

[Wario Wario Wario]

This is something I've pondered before, I've always liked the idea of getting to the end of Mushroomy Kingdom and then a rainstorm starting and causing a photorealistic Green Hill Zone to grow from the ruins.