Unfortunately, most armor sets are full of pretty necessary powers. That said, there are still some sets where you can get away with skipping a power or two.
Dark armor has a stealth you can skip, and you don't need to take both mez auras. Some also skip the rez, although it's a pretty nice power considering you don't get a traditional tier 9. You don't get knockback protection, though, so unless you get a -KB IO you'd have to use one of those freed power choices for acrobatics.
Willpower's self-rez is skippable, and since quick recovery is better than stamina you can get away without fitness (you can take it later on if you want to run expensive stuff like tough/weave, but you certainly don't need it at 20). This is probably the best armor set if you want build flexibility in the early game, since the fitness prereqs usually put such a squeeze on your pre-20 choices.
Fiery aura used to have a lot of skippable powers, but since they buffed the set a lot of those are now worth taking. The most skippable power left is temperature protection, but even that is decent for the slow protection.
On stone armor, if you don't mind relying on granite most of the time you can respec out of brimstone and crystal armors once you hit 32. Again, though, that doesn't help early game.
Energy aura has a junk energy/negative resistance passive that can be skipped, and conserve power is completely redundant when you have energy drain, so that's two skippable powers in that set. One even comes before 20.
Really, though, what'll actually help your build problems the most will be when the fitness pool becomes inherent in issue 19. Once you're not spending 3 powers by 20 on every build to get your endurance under control, builds are gonna be a lot easier to figure out early level. If you don't want to wait for that, then I'd recommend willpower.
@MuonNeutrino
Student, Gamer, Altaholic, and future Astronomer.
This is what it means to be a tank!
Muon is right.
It's pretty subjective what you want to take or not.
It seems to me you were, somewhat, confusing "I want that" with "I need that".
Anyway, I can't wait for Stamina to become inherent so I have more build room, but I think I'll need at least 3 more enhancement slots to throw around or the new power choices will be pretty much worthless unenhanced. 
Mind you, this question is posed by a person who doesn't really collect sets of anything so it's more or less focused on common invention and single orgin enhancements.
As of late, I've been making tankers and brutes. (and I'm tempted by scrappers and stalkers) The problem is that between most of the sets, it feels like it's an all or nothing choice. Skip one thing and it's like I will likely gut the set. Makes it kind of hard to choose when leveling.
So the question is, what set leans more towards 'you can get it later' instead of 'you better get it now' when it comes to the powers in it?
It would really lower my stress levels.