Just started reading The New Republic Omnibus and loving Mara Jade I feel like the Hands of the Emperor could easily fit into the current canon the same way. Sidious could easily have had assassins and servants Vader didn't even know about hell I know he did. He's just that kind of character.

I don't really understand why everyone treats the Inquisitors as the only way to adapt EU characters when clearly, they could be placed into canon just like before. Star Killer could still work as a secret apprentice to Vader. Yes, he says he wants Luke but that could be retconned as a lie he tells Sidious.

Mara Jade could easily fit as a secret assassin Sidious trained and hid from Vader for whatever reason. Maybe that's how the Hands of the Emperor could done. I feel like a lot of people over think and over complicate stuff when they are comparing current and old canon.

For example, they say Star Killer is overpowered I disagree I think it makes sense Vader would have an apprentice that could go toe to toe with him. I also think given he for a time thought his children were dead that it makes sense he'd subconsciously at least attempt to fill the void by taking an apprentice.