I've played two of those to compare side by side. Both were 16 INT builds (because obviously I wasn't trying to make things easy for myself) and both played fine on DOMINATING. The first one was a metal armor stealth sledgehammer build (with Body Weight Training and Nimble coupled with specialized Armor Sloping so I could stealth while wearing Super Steel armor) and the other was a 3 Will 4x70 "full psi" build. So, to answer your questions:
1&2) Perfectly viable, though what you start with for combat options will make or break your build. I'd roll it as either a high Will, high Int psi character (1), a low Will psi character (3) or a moderate Perception tin can AR (4 early, 2 later) or High Technicalities Versatility energy pistol user (6 early on, 3 later).
3) Make sure you get Disassemble, and pick feats to support whatever your main combat technique will be, as much as your stats allow. I'd also pick up Salesman if you've got a free feat slot, and depending on how silly you want to be, maybe max out Mercantile
4) depends on your difficulty level. On Hard and lower, all you really need to do is make a few merchant runs with high Mercantile to unlock top-tier inventories, buying whatever you want and crafting on the spot to resell your lower quality merchant fodder. While you're doing that, you'll eventually find that 160, 170 quality stuff and tuck it away to make your end-game stuff. On DOMINATING you have to be a tiny bit more careful because you don't have infinite money, so you want to only spend what you have to. You want highest possible quality armor, weapon, energy shield, and cloaking device. Anything else will be fine with whatever you've got laying around.
Of course, you could just play one of the full psi builds I recommended in my guide. They're 10 Int, by my recommendation, and can easily get enough crafting skill points to make everything in the entire game. And since you're psi, it sort of sticks to the inventor theme since even when you have to fight, you kill things with your mind =)