About the WoF driver at the entire system, it may be so :
Dism /Get-WIMBootEntry /Path:C:\
DISM.exe /Update-WIMBootEntry /Path:C:\ /DataSourceID:0 /ImageFile:R:\Install.wim
These 2 commands are a bit obscure to me for now but they seem to indicate a strong link between the system and a WIM file.
The DISM web page has been updated less that 10 days ago to reflect latest wimboot changes.
Now this is developper talking : i have been interfacing wimgapi in one of my software (CloneDisk).
If during your investigatings, you happen to stumble upon this flag (not documented yet) : WIM_FLAG_WIM_BOOT, I would gladly use its value