I'm looking into good alternate ranks for a void master that specializes in piloting and ranged combat.

I already took Flight Marshal.

Any suggestions?

The Void Master definitely seems to be the least supported flavour class thus far. Cold Trade Broker or Manhunter from Hostile Acquisitions are both worth considering. though. Cold Trade Broker lets you get cheap Exotic Weapons Proficiencies and a bunch of valuable Talents, and a Void Master qualifies for it at character creation. Manhunter has some amazing ranged and melee combat feats, and more Exotic Weapon Proficiencies (though more expensive)

If you could somehow fit in that whole Take Them Alive thing and such to space combat.. maybe.. but I'm honestly not seeing it, narratively. You're good at shooting people to take them alive, and thus you know where to hit a ship to take it out without damaging it...

Nah, nevermind.

You could maybe use the Manhunter for a good Navy-based equivalent in the same vein?

That said, the Voidmaster concept you're going for (OP), is.. unfortunately suffering from a lack of support. There's the Flight Marshal. That's really it.

Augmenticist or Arch-Heretek might be nice, but it greatly depends on your proclivities as a character, but upgrading yourself to become more and more as one with your ship or voidfighter might be interesting. Mind-Impulse Units plugged straight into the interface, pulling fly-bys employing Luminen Desecrations, Subversive Programmings, or Vile Intrusions.

If going this route, you should take a look at Cog Whisperer in The Navis Primer. It's perfect for it, and would give you +10 to Tests using whatever you bond with. Technically, you can go Cog-Whisperer without going the Tech-Priest/Augmenticist/Arch-Heretek route, but honestly I'd call any GM that would allow you to do that retarded, based on the fluff for the Elite Advance that it is.

Swashbuckler or Reaver might fit better narratively, but has little to offer without homebrewing. There's an argument to be made that Combat Flair could or should apply to Voidship combat, I think, but ultimately it doesn't and it would be an issue for homebrewing and an argument to be brought up with your GM.

Gland Warrior might fit both narratively and rules-wise, but only ever for the Lostok Augmentation. Other than that, it's terrible for a Voidmaster, so if you're looking at it, I'd ask the GM to allow you to take it as an Elite Advance, rather than replacing one of your whole ranks with it, because the options are really bad (imo, based on what you told me of your concept). But being a fighter-pilot with a built-in gland system of drugs... mite b cool.

Just my two cents.

Well, some details that I left out in the OP because I was in a hurry and I thought they wouldn't be all that important to the question (but it turns out they are).

The void-master in question is an Air-caste Tau (stats from http://ofdiceandmenrpg.blogspot.ro/2012/01/rogue-trader-tau-racial-characteristics.html )., which rules out Reaver. Extensive use of battlesuits (GM allows me to use pretty much all the Tau gear I could find around Deathwatch) brings the usefulness of Augmenticist into question (since Crisis suits seem work similar to Dreadnaughts, the Machine trait would be rather situational). Also, becoming more machine doesn't soud very Tau to me (although Arch-Heretek is an option I want to keep in mind).

I've also looked into Cold-Trader and Manhunter. First one's main selling point (exotic weapon prof.) is not that important to me (there are very few exotic weapons that are worth it over Tau weapons). AS for Manhunter, both the class's unique talents seem quite a bit on the strong side to me (easily exploitable with the right build).

In the end, I'm leaning a lot toward Colchite servo-master (refluffed to drop the psychic part of the control).