Yeah, I can see that being a concern, but 1. This is my personal printer, and 2, the lower chassis will have deckplates mounted shortly that will divert any liquid spill away from the PSU or the location the controller will be at. Any spill would either go down the center hole for the rail and down the two diverter plates, or over the side plates. There will be a fan vent hole somewhere in the side or the top plate, but I plan on putting a raised fan grille on the surface, and mounting it so the fan is somewhat offset of anything that would be adversely impacted by a spill. You can see the deckplates here before they are mounted. The front, rear and side plates are going to be similar once they are done, possibly with some sort of edge treatment (maybe a chrome corner band or something). I keep going back and forth in my mind about adding a belly plate as well, but the end result will basically be two somewhat sealed upside down shallow tubs over the melty electrical bits. Between that and my top secret vibration isolation rubber feet thingies I think that will mitigate the worst of the potential for disaster.
edit: the deckplate project is here: AO-10x top deck cover plates and Y rail Bellows