I am actually not a fan of "Challenger approaching" splash screens...
I like them, but I feel that being too attached to them doesn't allow for narration (and I was glad to not have them in SSE)
One idea I had :
- Spirits mode is a wall of "Cages" (reminding of Assist Trophy Hell), one for each character (even unlocked at base, to give more durability).
Once you select the fighter (his silhouette), fade to black, and CGI cutscenes play. They lead to different ordeals, be it Target Smash, baseball, etc. You have to win like 2 to three challenges to achieve each "mini-campaign". Then at some point in the middle of a cutscene, you would have ominous music start playing, characters looking around, and BAM, challenger appears, and you have to fight him.
- Ex : Ridley. You control Samus in a 1v1 against Dark Samus. Then you meet Mario and Mega Man, and Samus reveals her identity. You then control ZSS in a Target Smash or whatever for them to "acknowledge" you. Once done, you get back in the suit, and get in Ridley's lair. Maybe fight random villain team with Mario and Mega-Man as allies. The reveal trailer starts playing. Then you fight Ridley with Samus, 3 stocks.
Then cutscene, end of the reveal trailer with Ridley's Final Smash and ZSS coming out of the smoke to beat him. Then you play 1v1 with ZSS against Ridley in Giant/Metal/other form.
Once defeated, Final cutscene, and Ridley joins the roster.
Rinse and repeat for each character.
Looks like Classic Mode with CGI cutscenes, but kinda feels amazing to me. I can't bring myself to expect a full-on campaign like Subspace (and admittedly it has problems, with some levels being pretty uninspired... But the interactions, god !), with that many characters. Mini-scenes feel more doable.
- To get echoes you could have them duel their OG fighter. Ex : To get Lucina, you control Marth and beat her in 1v1 3 stocks, then control Lucina and need to beat Marth with the same ruleset. Simple but would allow you (and force you) to experience and find out which one you like most.
Obviously, other options would exist, like every 10 matches you unlock a random character by fighting them, amiibo unlocks, etc.
How would you feel about that ?
It may be pretty long, but I loved Subspace and it was kinda long too.
As long as you have other methods, I feel like people wouldn't complain as much. And of course you could still play the Spirits once again after the characters are unlocked, so no biggie.