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”.
