It's not really viable.
1)Obviously, there's no place to install it at the top.
2)For most AIOs, the pump is in the pump head, or cpu block. The interior of the Sharkoon VG6-W forces the pump to be the highest point of the loop... air makes it's way to the highest point of the loop.
It's a quick way to kill your pump, and bye-bye AIO.
3)For AIOs that have the pump elsewhere, such as in the radiator - that ultimately won't work either.
While the pump will be safe in the radiator further down, air is still up in the cpu block, disrupting the transfer of heat from the cooler cold plate to the thermal medium(the fluid).
This hinders the cooler's performance.
Sorry, but stick with air coolers inside that chassis.