In principle, sure, a story campaign within the Elite universe could be very good, providing the lore is used properly, current in-game events are involved and the actual storytelling/voice acting is spot on.
However, (and while I personally don't care) the moment you get a reward for completing the DLC campaign, is the moment the fabled words 'Pay 2 Win' will be shouted far and wide.
I would love, for example, to take part in another secret Sirius operation. Now in a perfectly ideal world, you could have story branch choices - do you go along with the operation and eventually allow Sirius to succeed in destroying something in an as-yet publicly unknown system with some Thargoid threat, or do you betray them and eventually take part in taking the attack force down?
Such stories would need to be completely separate from the 'real' game world, as it wouldn't make sense for Galnet to mention something that players haven't taken part in - or with multiple endings. So it would need to be totally self-contained. Except for the rewards. Rewards would probably need to be something that isn't particularly better than anything in the current game world, but perhaps could be unique in its appearance rather than function - I don't think that would cause too many grumblings - many paint jobs are impossible to just get without doing 'something', so I don't really see an issue here.
I think the bottom line, is that should you wish to not partake in a DLC campaign, then you lose nothing, and the DLC has no bearing on your particular game.