It would be great to access my paid streaming services channels such as Netflix, Prime Video, apple TV, Paramount Plus etc. (similar as I did with playon). I would like to see their play list/guide and record the stream/show. Since I would record them, I would not have a problem if these channels were part of the premium service.
I would also expect a secure login to my streaming accounts.
This topic has been addressed many times; so often in fact that there’s a dedicated paragraph for it in the feature suggestion guidelines:
In short, these requests are generally closed.
[Edit]
And what @OttoKerner said, too 
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Plex will certainly not allow you to “record” streams from other streaming services.
Otherwise it will get sued out of existence faster than you can say “aiding and abetting”.
2022 clean-up: provider integration requests are generally rejected (see above)
