What I've always missed is a storage port on the front, I've added it back on some of my computers, but it'd be nice to have n+1 HDD/SSD slot(s) in the front with a latch like a 3.5in floppy drive
I know a guy who uses old rack mount servers as workstations and he gets that. I guess it's a good option if you like wearing hearing protection at your desk as he does.