>>”The relationship to the original media (and thus the source tapes) is gone.”<<
Not at all true! But, I think I know what you are getting at.
And “destructive” is not the appropriate term if if that were true. Destructive would indicate that the original media files were changed and overwritten.
When a project gets returned from Color it creates a new Sequence in your project file that is a DUPLICATE of the sequence that was sent to Color adding the suffix ‘from color’ to the newly created sequence and linking the NEW sequence to the Color rendered media. The original sequence, links to original media is kept all intact.
That being said I’m in complete agreement that better integration into the “suite”… er, um, “studio”. I assume what you are referring to is how once you come back from color it is a HUGE pain in the hindquarters to make any editorial changes and then run those changes through Color. That would be a dream if that worked better. The best parallel that I can think of is Live Effects in Photoshop.