Unless you have a lot of disk activity in the background, I don't know how much that is really going to increase your performance. Your network throughput is going to be the bottleneck here, not the read speed of the drive.
Unless you have gigabit Ethernet in place, but even then, there are inherent speed limitations in the SMB/CIFS protocol that will fall short of the drive's speed.
That said, there is no reason you couldn't do it. Write up a little script to copy the files into tmpfs at boot, and have clients mount it read-only.