one thing to look at in regards to applicability
is whether or not the special effects would allow an EC as part of a powered armor. i've been examining this lately as i try to work up a powered suit character idea i've had.
the FRED rules talk about a very good point for determining if an EC is appropriate. look at whether a drain/supress could affect all of the powers at once. not all powered armor suits can match up to this requirement. the classic 'iron man' type of suit with a slab of metal for armor, boot jets, and several kinds of weapons isn't very good for an EC. a drain/supress might be able to affect one power, but not others, unless you're getting into some very exotic special effects for your drain/supress.
on the other hand, a more tight concept armor suit, let's use 'lady blue' from champions as an example, would have a concept for a powered armor that would could be easily affected by a single drain. her powers come from gravitic and/or force field manipulation, if i recall.
i've really had to rethink how to use EC's under the FRED rules, but i think being more strict is helping me build more realistic characters under the rules. it is awfully easy and tempting to slap a lot into an EC in order to save points. however, all those powers in an EC are also getting more vulnerable in some ways due to how a drain/supress affects all of the powers in the EC, and how powers are lost from an EC when it's part of a focus in the case of a typical power armor.
you need to look at what you're comfortable with here. if you feel your concept of a suit wouldn't lose several related powers from a penetrating hit or a drain/supress, then maybe an EC isn't the way to go. standard points in FRED are higher, which gives you room to eliminate a number of disadvantages while keeping the same rough power level.
also, in looking through the sample characters for 5th edition products, i've noticed that the technology powered armor types do not have elemental controls as i remember. multipowers are common, but the non-attack powers that normally would be placed into an EC, such as flight, armor, force field and such are all on their own as seperate powers.
-v