Lenovo storage driver difficulty

One of my projects entails deploying a Windows image to a group of laptops, all of a certain Lenovo ThinkPad Edge model. I have successfully deployed to them in the past with normal WDS, but this time I'm trying to use MDT, which (though the image is ultimately served by WDS) does not produce WDS boot images.

The problem is that the MDT image - the thing that presents the UI that gives all the options and the wizard - doesn't seem to contain drivers for the storage controller. MDT can never see the disk; DiskPart says that there are no fixed disks. I've jammed all the drivers from the Lenovo Update Retriever for the model into the image and tried putting in the drivers from an installed OS, but the problem persists.

I have also tried all combinations of UEFI vs. Legacy booting and AHCI vs. Compatibility SATA mode. Changing those settings makes the BIOS/UEFI startup screen look different, and one combination makes the disk appear in DiskPart, but then MDT hangs before it can show the wizard. I don't know what's going on here.