The future Sentinels in X-Men Days Of Future Past are clearly shown adapting to powers thrown at them by copying them. Isn't that what Rogue's DNA would allow for, not Mystique's? Mystique can just change appearance, not copy powers ... right? So why would study of her mutant genes allow for the abilities of the future Sentinels?
Mystique can just change appearance, not copy powers ... right?
As far as has been shown, yes, that is correct. At least, mostly.
So why would study of her mutant genes allow for the abilities of the future Sentinels?
There were two massive improvements shown:
- The seeming ability to change power sets (more on this in a bit)
- The ability to change their appearance, materials, mass.
The second ability is pretty evidently derived from Mystique's abilities. The power set change ups aren't definitively being copied or added on the fly. Remember, by this point, the Sentinels have been hunting mutants for a very long time. It is entirely conceivable (and even likely) that Trask Industries has been adding to the Sentinel's capabilities and weapon sets over time - giving them the necessary abilities to handle the mutants they come up against.
But without Mystique's abilities giving the Sentinels the abilities to reshape themselves, they wouldn't be able to stand up to the mutants as well.
We can't forget that Trask was legitimately a genius. Mystique's DNA was instrumental in allowing the Sentinels to adapt, but he certainly didn't just copy and paste that one trick and call it done. Odds are he saw something within the function of Mystique's ability that jogged his imagination, and then his own genius (and that of other researchers after his death) allowed them to go from "changing appearance" to "changing ability."
Think of it like the old story of Newton watching the apple fall from the tree: what he witnessed (i.e. an object falling due to gravity) simply gave him the spark to eventually describe the patterns of not only gravity, but inertia and a number of other laws governing the motion of objects in general.
Mystique's ability gave Trask a mechanism for rapid physical change. The nature of those changes, and the abilities available to the Sentinels from then on, was no doubt the result of further study and decades of refinement.
We'll actually Rogue absorbs life force, which in mutants, is essentially their powers, Mystique's shapeshifting powers allow her shift her entire atomic and molecular being, in other words, she can shift her body to adapt to anything, which is what Trask wanted her DNA for, to give the Sentinels the ability to adapt to any mutant power, not copy because that's not what they did. Notice when they fought Iceman, Bishop, Blink and Collossus, they adapted to their powers and learned how to overcome them, they didn't copy their because what good would come from copying their powers and I'm sure the Sentinels were learning machines as well and Mystique's shapeshifting powers allowed them to physically "learn" to adapt, as that is essentially what Mystique does
It is a plot hole. Xavier says powers of "transformation" gave what Trask needed to create weapons which could adapt to any mutant power. But this makes no sense because we know Mystique's transformation does only happen at appearance level.
Xavier: They captured her that day. Tortured her. Experimented on her. In her DNA they discovered the secrets to her powers of transformation. It gave them the key they needed to create weapons that could adapt to any mutant power and the result is the machines that have destroyed so many of our kind were created and it all started that day in 1973.
Mystique's DNA by itself would allow them to shapeshift. But this is a feature useful for spying purposes eg. impersonating other people. Mystique's powers does not give her better fighting abilities. (unless you turn your hand into a blade to cut your enemy)
The premise is that Mystique's DNA was researched and allowed Trask to figure out how to do every trick in the book. But this is far fetched, because Mystique's power is changing physical appearence, not mimic the power of another mutant. With that logic, they could start with a bukalemun DNA and come to same end result :) Why you would need Mystique at all?
Also, AFAIK, sentinels are not biological entities. So the only way to use mutant DNA would be figuring out how the power is physically manifested and try to reproduce it using electromechanical ways using hardware. If this was possible, this means you could make a machine which can read minds and control people if you had Professor X's DNA (that could make a good home automation system). Make an excellent fridge using Iceman's DNA or great grill using Pyro's DNA. :)
Even more, if Trask already figured out how to read mutant DNA and copy the powers to sentinels, why would they need Rogue who can only temporarily hold/mimic another mutant's power by touch? That would be redundant, no?
If Trask needed to collect powers one by one, and sentinels did not immediately get all the mutant powers at once. Then mutants would have had plenty of time to deal with sentinels before they became too powerful.