First thing... I hate penetrating vision. There is a reason very few heroes in the comics have it. It makes it too easy to get around plots

Even superman doesn't use his very often, and when he does, he's concentrating on it. So, while I shall expound in various ways, there's a big no to penetrating vision unless you have super senses relating to sight.
Mimic
I'm going to just say no to penetrating vision (mainly because it is a pain in the butt to me and it should require super senses and even then I will constantly come up with ways to foil it so I don't have to think around it). Your magnetic wave have nothing to do with sight, and it just doesn't make sense to me to have you suddenly develop a new ability based on you not being able to see through a window once.
For your stunt versus extra thing, remember that stunts are used in place of their base power, and never at the same time. Even if you were to take snare as a stunt, until the snare is broken, you would not be able to activate your force field. The same holds true for suffocation, in that unless you stop the suffocation, you cannot activate your force field. To work any other way requires the abilities to be extras.
Take a look at Tyroc. He has an energy blast with a stunt of paralysis and a stunt of slow. He can blast someone and slow them down, but he can't then blast someone else and hurt them. While he's using slow, a sustained power, he can't use any other form of energy beam without first getting rid of the slow. Same for paralysis. If he wants to be able to paralyze someone and then blast them while they are paralyzed, he'll need to take an extra.
Bank up or buy a partial extra of snare on force field. Would be tres cool to see you encasing foes in big force field bubbles
Elementor
Unfortuneately, it is an
extra of super speed, not a stunt. Since I use alternate rules for incorporeal, it may be less desireous for you. To move through objects with more hardness than your power rank, requires a DC10+hardness power check, just as if you tried to move through a force field. This means you will need an 11 to move through glass; a 20 to pass through steel. It's very cool though, in that you also have protection up to your incorporeal rank against all attacks but one kind (cold sounding like a good one for Vince), and can sneak hotdogs out of bar kitchens if Raisa punches you. Because I know you'll ask...
If you try to move into something, but fail, you'll just bounce off. You'll have to make a stun damage save (unless you were going through a wall of razor blades, and lets hope your GM doesn't think of THAT). What I do for hardness (say of a building) is average it out. Just because the building has steel beams, doesn't mean it has hardness 10. It is likely more like brick and stone, so hardness of 7-8. You'd avoid the steel beams because you can see them as you approach. That way, you won't knock yourself out running through a building and die trapped within stone, unless there is a sudden change of hardness, and I can't see that happening with the exception of a vault or something like that.
Still, as far as extras goes, I'd say getting a partial extra on incorporeal would be good, but I'd look at building it up to super speed rank asap to make it the most useful. I'd say an average for a house would be 5 hardness. For a major building, 7-8.
You actually don't have any super senses. You just have some wierd mutations in your eyes. Also, penetrating vision is not required for incorporeal, since you only become non-incorporeal at your leisure, and when incorporeal, I treat it as if you can see well enough for normal movement. I really don't see any reason for you to suddenly develop that ability. See invisible would be fine though. Another no to penetrating vision, sorry guys, gotta save my sanity.
Other
I'll be checking with everyone on the benchmarks I have tomorrow, in case anyone wants to change them or add them.