That's possible with the following registry modifications:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\SPVDPort]
@="Service"
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\SPVVEngine]
@="Service"
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\SPVDPort]
@="Service"
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\SPVVEngine]
@="Service"
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SPVVEngine]
"Group"="SCSI Class"
This adds the RAM Disk drivers to the list to be loaded with Safe Mode and Safe Mode with Networking.