Yes, in theory you could have an AUTOEXEC.BAT that loaded the ramdrive, then copied the OS to the new ram drive (which would be seen as, for example, drive D:, or whatever the next available drive letter is).
In practice I don't know how useful this would be, since the speed you gain from this would more than likely be offset by the long copy time at boot up. You can still only copy file to the ram drive as fast as the HD can read.
Also, I'm not sure what the size limits on those ram drive are, seems the built in DOS ram drive program was very low limit (like 8 megs or something!) The shareware programs would probably be higher.