While I don’t see this as a feature of Cubase itself – it seems to me it would more likely come in plugin form – this is pretty much exactly where I stand on the potential use of AI in this context.
For perspective, I am also a keyboard player (and singer and songwriter and …) with a project studio. I am decidedly not a guitar player, strings player, brass player, etc. Over the decades, though, I’ve played and/or programmed all the instrumental parts on all except an extremely small number of my recordings. It is something I do partly due to financial limitations and partly because of creative control considerations. I can remember a few times when others have volunteered to play guitar on some of my recordings, and I took them up on it, but I wasn’t happy with the results. It’s not that they weren’t solid on their instruments, it just didn’t fit my vision.
Guitar has been a special challenge because many of my songs are either guitar-centric (despite my being primarily a piano player) or at least feature guitars as important elements. I can generally play finger-picked parts quite believably on a keyboard (I’ve even gotten compliments on the excellent guitars from reviewers on some), especially with modern virtual instruments. Electric guitar leads can be a bit tougher, and more programming is typically needed to add some of the nuances. But strummed parts are the harder thing, especially on the getting precisely what I want side of things. I’ve used a combination of loop-based virtual instruments that do chord detection (my first on that front was Steinberg’s Virtual Guitarist – these days it’s mostly either UJAM Virtual Guitarist or NI Session Guitarist products), but there’s a lot of work involved in finding something close to what I want, and doing any manipulations to get it closer still.
If there were something out there that could get me a lot closer a lot more quickly, I’d definitely be interested. I think my vision on that on the strumming side would be along the lines of I let it know rhythms I’m looking for, along with the chord changes, and it would give options that make believable guitar parts out of them based on its LLM equivalent that had knowledge of what guitar players do (which is quite different from what programming strums makes easy). For leads, it might be that I’d record a MIDI part, but it would add the nuances that relate to a style I described.
Oh, and while I’ve been talking about guitar parts here, I’d probably even be more interested in something that did the equivalent for pedal steel and fiddle because those are two instruments I’d like to use more but have never been able to get sufficiently believable. For example, with the pedal steel (I’ve had the Wavelore Pedal Steel since it was a Gigasampler instrument, though I now use it in Kontakt), there is just a huge amount of programming needed to get truly believable parts, and you actually have to be pretty knowledgeable about pedal steel playing techniques to know how you should be programming it. What I’d like to do is just play a part on keyboards, and have it get mapped to believable pedal steel techniques. Personally, I’m less interested in wind instruments because I’ve been able to do those much more easily with a combination of really solid virtual instruments and a wind controller (I played clarinet and saxophone in my teens and early twenties, but my tone on those, especially saxophone, is way better using a wind controller and virtual instruments).
Again, though, I really don’t see this as an integral feature of Cubase. Maybe it could be one of the “extras”, the way HALion Sonic and various included libraries are, though I’d expect it to be more like teaser level products if something of this sort were included in Cubase as something more specialized would be warranted for more depth and breadth. I think most of what would be needed from Cubase may already be there, for example in the ability to use the chord track to generate MIDI for instrument tracks, general MIDI recording/programming capabilities, etc. I’d see the AI aspects coming in at a specific virtual instrument level, be it for guitar, strings, singers, or whatever. That’s where you’d describe any specific aspects of what you’re looking for to feed off the MIDI (and/or perhaps audio, for example in the case of virtual singers or humming a bassline or whatever).