It would be great if we could for example import all PC titles available under Xbox Game Pass Or Ultimate. Same for Xbox only titles. That would help users see if a title is already available under a subscription and prevent accidentally buying it outright.

Also (ideally) could do the same for Orgin and other game subscription service titles available currently.

I can understand where it would be helpful to have a means to check against accidental unneeded game purchases, but I don't think it'll work terribly well in practice. At least, not via a collection import.

The problem I can see with that approach off the top of my head is that things like Gamepass are fluid and change frequently like many subscription services. Sure, you could import everything available via gamepass into your collection one day, but three months later, you might not still have access to all the titles since there will be those which have rotated out and your collection is no longer accurate.

It's a neat idea to have an amalgamated list of "free" games included in the various subscriptions out there, and I'm not sure one actually exists. Something akin to justwatch.com, but for games.

edit: I can't vouch for how safe or accurate/useful this is, but I did find this after flexing my google-fu a bit: https://aligueler.com/SubscriptionInfo/