Recent research on #ShinySnake #s400 shows: Yes, with a bit of custom modification of the case, #AIO / #LiquidCooling should be possible (in the top).
Modifications may include: Raising the case by up to 2 cm, to accomodate space of 49 - 54 mm.
OR just cutting open the top / drilling hundreds of holes into it, for proper airflow of fans, and then mounting the radiator right on top.