This would have been interesting, but unfortunately, it will be difficult to format the volume without a drive letter.
However, on Windows Vista and later, you can redirect a folder content into a ramdisk by defining a symbolic link to the ramdisk volume with the command mklink /d (type mklink /? in an elevated command prompt for details).
So, for example, if you want to redirect a folder like D:\my_folder to a ramdisk R:, you can try in an elevated command prompt (D:\my_folder must not exist):
mklink /d D:\my_folder R:
You can even hide the drive letter of the ramdisk in Explorer by using the "General Settings" of ImDisk Toolkit available in the Start menu.
Just FYI, on 2000, XP and Server 2003, where mklink is not included, you can use my "junc.exe" tool to do the same:
junc D:\my_folder \??\R:
or, directly to the root directory on the ImDisk device:
junc D:\my_folder \Device\ImDisk0\
Junc.exe is available here:
Another idea. I have found that format.com, chkdsk.exe and a few others accept a few more things than A-Z drive letters. For example, I have a script where I create an ImDisk drive, mount it to a subdirectory and then formats it using a temporary drive letter. I create and remove this temporary drive letter with my dosdev.exe tool before and after the script calls format.com to format the virtual disk. As drive letter, to make sure I don't interfere with any existing drive letter, I use Ö: which, for some yet unknown reason, actually works with format.com. But Ä: does not work, for example.