I like the idea of Wu, mage of life, being responsible for Bugbears and Hobgoblins. There needs to be another though. So far we have three races of goblinoid; Bugbear, Goblin, and Hobgoblin. There needs to be a hidden fourth bred in secrecy deep underground... do you think Nilbogs would work?
Given the scale differences between Goblins, Hobgoblins and Bugbears, a 'fourth' could continue in that vein and be Huge or larger, a lumbering Giant-goblinoid, *or* it could go in the reverse direction, and be a horde of chittering diminutive fey-goblins riding oversized wasps using Swarm rules, *or* it could go completely sideways and be something totally different, like a goblinoid doppleganger, able to infiltrate human society, or a goblinoid quadruped usable as a mount by the others, or a purely psychic entity that seems like a goblinoid ghost (but not undead, being more of a malevolent incorporeal fey) using curses and fear attacks.
The thing about Wu is that he prefers to use traditional breeding combined with magical serums to enhance the natural capabilities of beasts. In other words, he's responsible for dire animals. I actually have a different plan for chimeric animals like owlbears.
That would make the larger goblin-giant or mini-swarm-goblins more likely than the malevolent incorporeal psychic fey-goblin.
A 'Legion' concept that has a pack of a couple dozen goblins that can merge together gruesomely and become a Huge giant would be interesting to see. As the giant lumbering creature with it's twisted limbs takes more and more damage, it becomes unable to sustain it's combined form and breaks apart into a dozen surviving goblins... Perhaps, in giant form, it can spit out normal goblins as projectiles, or absorb other humanoids it grapples into itself to heal!
Magus Wu, mage of life. He breeds dire animals and races of super soldiers and he is a master of unarmed combat.
Magus Aare, mage of death. He strives to create more efficient undead. Some say that his "hospitals" can produce a thousand zombies a day.
Shadow goblins, hobgoblin 'death knights' and bugbear spectres certainly sound like potentials.
If you don't want to use standard undead completely, or want some lower level versions that aren't skeletons or zombies, you could have him be a necromantic 'efficiency expert,' taking a single humanoid corpse and;
1) draining it of blood, then saving the blood to animate into a cold ooze-like undead creature that seeks to flow up and smother living creatures, so that it can add their cold, dead blood to it's own.
2) very carefully flaying it's skin off, preserving it as a solid sheet which is then preserved in natron salts and alchemical compounds to become leathery-tough and then animated as a sheet of skin that attempts to wrap around and constrict people.
3) remove the muscles, organs and viscera from the bones, animating the mass as a fleshy ooze-like creature of pulsing blood-draining veins and arteries, crushing muscles and squirting digestive acids.
4) animate the skeleton left over.
A single humanoid body could make four weak undead creatures. The Viscera would be the most damaging, with the blood-drain and acid adding to it's enveloping crushing damage. The Blood Weird and Skin-Wight would both be too feeble to actually cause damage, although either can smother someone in a grapple, or restrain them, to make them easier prey for the skeletons and viscera.
An alternative to the Blood Weird (or perhaps yet another option) would be to infuse a part of the dead humanoids spirit into it's shadow (perhaps just the 'echo' that is left behind and can be contacted via Speak With Dead), creating a weak form of Shadow, that has no strength-draining touch, but can 'grapple' someone incorporeally to blind them, making them easy prey for more corporeal undead.
All these sorts of undead could be a single HD, or even a half-HD (in the case of the blood or shadow creatures), although they would be hard to damage (the skin-wight would have DR 5 / slashing, for instance, since hitting it with a club is mostly a waste of time, as is sticking an arrow through it, while the blood creature and the incorporeal shadow would be even harder to damage physically).
Magus Raux, mage of the inorganic. He creates diabolical machinery and experiments with grafting his devices into living and undead test subjects. He is rarely seen, but some say that he has transformed himself into one of his own artifacts.
Seige engines sound very cool, as do armor-plated goblinoids that turn out to be grafted into their armor...
I've never heard of Orogs, or whatever they are called. Can you tell me what book they are from?
Orc / Ogre hybrid. You could just make Orcs with the half-Ogre template.