Here's some perspective for you-
That video is 13 years old and the content running Garageband on an iPhone4. I don't know if they had automation available on it then but I know they were doing it 6 years ago, so if outdated iPhone can run multiple tracks of audio and VST, accept/send MIDI, automate effects/volume/EQ, I'm quite certain an app written by Line 6/Yamaha group in 2025 could pull it off just fine.
As for the stem splitter, there are websites that do it for free now using AI and there's sites you can pay for that'll do high quality splitting-
I think it's safe to say Line 6/Yamaha has the resources to pull this off. Especially considering Eric's reply to my hopes for the ability to alter the speed of songs in Showcase and how it currently sacrifices the audio quality, I'm going to assume that there's a barrier they won't drop below if they're going to put it on this.
If you can't see the usability of some of these features, I don't even mean this in a dickish way, but I'm going to assume you have little experience outside jamming in the house. And even IF jamming at home is your thing, one of the most highly requested features is some kind of way to play audio through a modeler so people could jam along with songs, being able to remove all the guitars in your favorite songs to jam with at home, while your fancy pedalboard switches all your effects, I'm sure there's going to be more than one dude standing in front of a mirror when a solo section comes up and the wife isn't home so they can really crank the lead preset.
From a live performance perspective, that thing is fucking nuts.