Well, the cash gains from Slicing got nerfed quite a bit a patch or two ago. Since you have Scavenging, you can take anything that compliments it: Armormech, Armstech, or Cybertech. Also, without the proper Mission Skill for your Crafting prof, you cannot make any rare (prototype) or epic (artifact) quality gear unless someone has the mats for sale on the GTN (depending on your server they may or may not be available, and may or may not be overpriced). If you can grab the Mission Skill on another toon (say your BH takes Cybertech and your Agent takes Armormech w/ Underworld Trading) then you're okay.
I'd personally go with Cybertech, as it's the only prof that can make Ear pieces and Armoring, and I believe it may be one of two that can make Mods. You can also make Starship Upgrades and Droid Parts (so your ship droid can actually be a useful healer!).
I took Armormech on my Powertech and am kind of regretting it. I say "kind of" because it's very nice to be able to make off pieces like a belt and gloves before you can get a moddable one, and you can also make some very nice gear for Mako - whose healing is invaluable early on. Haven't looked at the ending recipes, but I'd imagine you can make moddable armor pieces at 400. The only thing I don't like about this is that all you can make is armor - no mods or anything else special.
Armstech is said to be bad by a lot of people, but you do get access to making your own Barrel item mods. At 400 skill you can also make your own orange moddable guns.