Unless they update the sampler to react to Midi CC(10) pan messages then the main problem here is that Cubase has no region/clip automation either. So your only choice is to automate via the main timeline. So while it can be done, it’s not great for elements that you want to loop across the project - which i’m guessing is your frustration? and i agree with it.
Region/clip automation needs to be added really, but i appreciate it gets hard to handle with that and timeline automation clashing. But most other DAWs do it fine.
On a helping hand,would this be of any use to you? :-