Not wishing to sound needy, but is Tupp good to go?
Also, why is playing a duplicate so bad for you guys? Just because they take on the same role and mantle doesn't mean they're the same person or whatever. Psykers have a wide variety of disciplines they can use and there's more the the Sororitas than just Sisters of Battle; its all there if you're willing to go look for it (which isn't that hard) and also willing to make a character that isn't a carbon copy of someone else's.
Basically no Astartes at all at least due to right now, being chalked up as Karthis lacking enough inquesitorial influence to get on as part of his retinue.
As for weapons/positions, just be reasonable and you should be good. Don't go carrying about something like a dozen digital weapons, a trio of conversation beamer and chainswords coming out of the ass as Daemonhost or something.
Dude, it doesn't matter what kind of Inquisitor you are, if you tell a Space Marine "Join my retinue" then they're gonna fucking join it, because they know they'll get horribly fucking Exterminatus'd if they don't.
That being said, I would love to play a Mutant or abhuman. Failing that, something Mechanicus related. I know the Inquisition and AdMechs aren't on the best of terms (Inquisition tolerate them because the Imperium would fall apart without them.) But the oblivious one that only cares about carving up every bit of tech that he finds sounds like fun.