I think I've found a more recent version of the ADK.
At the bottom of this page:
Windows 10 Technical Preview hardware tools
there's a link to ADKSetup.exe
On installing it I get version 10.0.10041.0 of the deployment tools.
There also appears to be some documentation here
Get involved - Windows 10 hardware dev
within the Customize and Manufacture sections. For instance DISM is documented within Manufacture and SIM is covered within Customize.
The new Imaging an Configuration Designer is covered more here:
Windows Imaging and Configuration Designer (Windows Drivers)
I probably won't get a chance to play with it for a while myself though. (I'm also having issues with Windows 10 build 10041 - it keeps crashing on my old hardware so something is different to 9926 which was much happier; so I may wait for the next ISO.)