its a massively genius move if your case allows it.
Take the Lian Li O11 EVO. Once you water cool it and put a radiator in the bottom. Its nigh on impossible to reach the usb sockets at the low end of the board without ripping out the radiator first.
Plus reaching all the PSU cables like the 24pin ATX can be difficult as you navigate your hand inbetween hard line tubs. This is something I have wanted for years, but it will be unusable for some Chassis.