Alright! Well, after switching to AHCI mode in the BIOS settings, hotswap seems to work. When I have 3 drives, pull one out and do a unit rescan, only two drives show up. When I put it back in and do a unit rescan, three show up! Now, I haven't tried this with a software raid, but it seems this should work, now!
This will be great if it works, since we won't have to spend money for a hardware RAID controller on the smaller boxes.