Dear Princess Celestia,
My full notes will be travelling by courier, but I wanted to send you a short summary of my findings before the university tears into it. Rose has been extremely cooperative, and, in public, I will be maintaining our view that integration of changelings is possible, however her abilities are terrifying. I would not say that Rose herself presents a threat to Equestria, but that is because of her individual temperament, not any inherent qualities.
Changelings
Changelings are small, quadrupedal, and have a roughly equine shape. Overall there is surprisingly little of note in their biology. They operate on well known vita principals, with a great many similar, if not identical, internal structures. Changelings can, and do, eat regular food but it appears that emotional energy is required for higher functions, and this energy is quickly drained by the use of spells and other magics. As far as I can tell, changelings do not have their own internal wellspring of magic, and all the powers they express are the result of scavenged prime energy.
There has been debate as to whether changelings can really cast unicorn spells, or whether they just mimicking the effect through manipulation of prime magics. I can confirm that their telekinesis is an arcana effect, but they can also cloud walk like a pegasus, bend space and commune with nature like an earth pony, and use pyromancy spells. I convinced Rose to emulate some zebradian forms of magic, which she did with relative ease. Alexis has said repeatedly that Chrysalis wanted to steal the sun and I see no reason why Rose could not do this, beyond mere inexperience.
Drones
Rose’s drones have the approximate intelligence of a well trained dog and the vocabulary of a parrot. Judging from discussions with Rose, she believes her drones are unusually smart and far more capable than Chrysalis’. They seem able to operate on their own for extended periods of time and even devise complex and well reasoned plans without her input. When a large number of drones gather they can form a hive mind, allowing them to communicate instantly and react as a unit, thus increasing their decision-making capabilities.
Drones, while capable of magic, seem to be quite poor casters, able to do little beyond basic energy blasts, flight, and aping the native skills of ponies. They are also, somewhat surprisingly, quite poor at disguising themselves. Often they miss or misinterpret many major features of the pony they are trying to emulate. While they will pass a cursory examination, they could never hope to impersonate a specific pony for any length of time.
Rose
Rose is similar in appearance to Queen Chrysalis, baring some differences in colour. She is set apart from the other changelings by two factors: her intelligence, which is the equal of any pony, and her control over magic. Rose... is an alicorn in all but name. She does not understand magic, but can cast anything that I explain and at a strength that rivals my own. She is limited in her exertions only by her access to emotion as a power source.
Much to my surprise, Rose does not lay eggs, but shapes them. With enough prime she can pluck them out of the aether and they appear to be viable without need of a mate. I have not yet had time to examine the lifecycle of a young changeling, but given Rose already has many apparently adult drones, they can either grow extremely quickly or be summoned in an adult state.
Conclusion
I can not overstate how large a threat the changelings could present. Rose seems reasonably balanced, empathic and is limited by her extreme youth. Chrysalis has none of these redeeming features and has a large supply of power in the form of the subsumed buffalo empire. I know what the official conclusion of Chrysalis’ threat was, but after my research I can not agree. Chrysalis is a real and imminent threat and we must respond with all possible force in the event of a second attack.