(Yes, this is from the Psionics in DragonMech guy). I was browsing through my old Magic of Incarnum book lately (so sad that I never got a chance to use it), and I realized it really could have a place in DragonMech. Think about it. With the gods under siege, souls have been getting waylaid en route to their final resting places. Devils, demons, and angels compete for souls, no longer controlled by any gods they may serve. And what is incarnum but the magic of souls? The book even suggests introducing incarnum as a new magic, just recently unleashed by some cataclysm that threw off the birth of souls. Imagine if not all souls that fail to make it to the afterlife are stolen by fiends or angels. Some just get lost and linger. Similarly, some souls are knocked astray before they can even reach their body for birth. (On a side note, that could make this threat even more dangerous. Devils and demons are stealing preincarnate souls now, and people are being born without souls as a result). A new breed of magic is born, and with its strange resemblance to blue steam, it might attract the interest of a different breed of mage.
So, what might we see if incarnum is tapped by the heroes of DragonMech? Well, I've already previously written about the Tenth of Nine, a prospective lord of hell hoping to claim Highpoint as his own realm, with the promise of plane-shifting the domain to hell once it's his. I've always envisioned the Tenth of Nine as a fiendish steamborg, fueled not by coal, but by the souls of damned. So it's not that hard for me to imagine a steamborg whose engine runs off of incarnum. The flow of so many souls through them helps ward off the loss of self that so many steamborgs endure, but sometimes the babble of so many voices makes them lose themselves in a different way. When an incarnum-using steamborg fails a Lose Self check, they do not become overly mechanical in their thinking. Rather, they lose themselves amid the many other voices they welcome in, temporarily developing a multiple personality syndrome.
Another useful facet of incarnum is that it's normally shaped into a physical form. I could see a mech jockey being able to craft gears out of incarnum, enhancing their patchwork repairs so that temporary hit points are granted which last until used up or until the patchwork repairs fade. Moreover, mech jockeys, coglayers, and steamborgs offer new kinds of souls to channel into soulmelds. A meldshaper may channel the impulsiveness and agility of a mech jockey, the skill, knowledge, and inventiveness of a coglayer, or the lost humanity of a steamborg (shielding him- or herself against mental attacks of all sorts). And no doubt bad things happen when someone tries to channel the souls of lunar monsters, hoping to gain advantage against them and instead becoming one of them.
I am Omnirahk, half-Rahkshi ("Omni") of the WotC forums. I consider "Psionics in DragonMech" (see my website) my greatest contribution to anything d20 so far. At least, it's my most successful topic.