> For years I’ve been complaining that I can’t easily use my private iPad with my company Mac because they have separate Apple IDs. Things like sidecar for a quick virtual whiteboard are basically impossible.

This is kinda what Managed Apple IDs are for - the work 'owns' the Apple ID it puts into its management profile and can set policy. Apps write into a separate storage container which the company could remote wipe, without affecting the rest of your personal data. If they want to disable things like sidecar, they can do it.. for the corporate apps/accounts/web domains.

I'd' generally assume the multi-user aspect is worse (because face shields and prescriptive inserts) so generalized multi-account is pretty low on the priority list.