[@Ghost Queen] Sounds like a plan to me.

[@LancerOfBlue] With regards to what magic is, an assumption that it's an all-encompassing field of sorts will suffice. Regarding your ideas, uhhh... this may need discussing with Solaris before anything is confirmed, but I believe I did point out previously (if I didn't, I am now) that transformative magic is extraordinarily difficult for the same reasons that simply blowing up a person's head is difficult - you need to manipulate [i]all[/i] of the substances involved in the transformation, and especially the need to alter one's genes from human to animalistic and back was a nigh-impossible feat, since for the majority of history humans didn't even know genes existed (though now that they do, a VERY sufficiently-learned individual could feasibly attempt to create a spell that turns them into a chimera until they want to switch back... with varying success, ahemhem).
That said, the treant idea is actually more viable: it's established that rituals can be used to, for instance, become an immortal skeleton, and I imagine a similar ritual to turn oneself into a tree person, or rather put one's mind into a tree whilst shifting it into a form the user can actually move around, might be similarly difficult in different ways, but ultimately plausible. To wit, the person so altered would probably live longer than a normal human, but they'd still be limited by the tree's natural lifespan, and would obviously be somewhat out of luck if, say, an oak-killing fungus started sweeping through the ranks of the local ents.
Just as a final note, animal handling skills ought to be trained rather than an innate part of a druid's magical abilities, since again, transformation is difficult.

[@Kafka Komedy] Bionetics might be converted into innate parts of the Husk's biology. Cybernetics would just be ejected from the body as it morphs. The main thing about Husks is that their innate abilities- at least for the "sentients", in this case PCs, though that may differ from the understandably-weaker drones- are more on par with humans and chimeras [i]including[/i] cybernetic and bionetic alterations, whilst consequently being stronger than biomod-less chimeras, and [i]way[/i] stronger than unaugmented humans. Draconids set that up by being flat-out stronger, in exchange for it being real difficult to install either cybernetic or bionetic modifications; Husks do it by being potentially far more diverse, not only having access to the perks of being a zombie insect, but also a pool of powers that they outright don't need modification to access, potentially up to and including the passive magical effects Draconids possess if they get lucky (reeeaaaal lucky, though, especially if it's both flight and a breath weapon they're receiving). They can have acid cannons innately; they can have wallclimbing spider powers innately; and so on and so forth, pretty much covering the entirety of viable biomods and then some.
As for magical aptitude, I can imagine a sentient Husk created from a mage is more likely to have magical aptitude, in much the same way that a mage is more likely to give birth to children who are mages - not guaranteed, but as has been said, the chances of a magical lineage continuing are greater than a new line of magic being birthed from a previously-powerless one.