I'm working on a somewhat related product (except bringing this assistant capability to all apps on your computer, all browsers, and using mostly on-device ML...waitlist in my profile in case you're curious)
What we've discussed internally is having two modes for the cases where we do need network connection:
1) A turn-key, use-our-OpenAI/HuggingFace/whatever proxy that doesn't store anything, just adds our token and pays for it on your behalf
2) Bring-your-own key for each service
The fact is that most users who just want to use these kinds of productivity tools might not have their own OpenAI/Azure/etc account, so offering option 1 and even defaulting to it is right for most end-users.
I think XP1 is making the right call here with this default, though offering #2 would be nice!
(edit: added Github link to XP1)