Theoretically, yes. Water can heat no higher than 212, at sea level. Sand and ceramic/clay have no such limit. Were the cooker to spike a temp--say a large buried chunk of wood ignites at 3 a.m.--a sand (or similar) arrangement will heat and just keep heating as long as the heat is applied to it. (This can happen at the beginning of a cook as well--say, due to a Standard Method start or an overly aggressive Minion, or a bunch of wood that spontaneously ignites.)
The big deal, however, is that there has to be sufficient oxygen to fuel the fuel. If the cooker is set for the night--and this means established for at least a couple hours--there isn't usually much to worry about. A cooker that has just enough fuel going and is being provided just enough air to keep it going can stay stable for a long time, hence the set-and-forget quality of the WSM.
This supposes that potential wind/breeze problems are averted. A breeze that wasn't present during the start-up and establishment of the cook can cause problems if it shows up at 3 a.m. and, say, there are buried wood chunks just dry enough and positioned to burst into flame. (Conversely, a little sustained breeze that was present during the establishment of the cook, that quits later, can also affect cooker temps, oppositely of course.) Still, even if spikes occur, they are rarely cause for concern, even with sand, though water handles them better. Unless you are cooking something that is extremely temperture sensitive--not likely on an overnighter--then, unless a log has ignited, should a spike occur it's rarely a problem.
The vast majority of my cooks are done with a foiled empty pan. On the cooks I use something I use water because it's convenient and predictable. That (and the above) said, one can get used to factoring in numerous variables rather than controlling them, and have successful cooks nevertheless. (E.g., I cook in the direct sun and in the rain (no shelter) and fully exposed on all sides (no wind block). I'm used to it. Two things I never do: I don't use large wood chunks--anything fist size gets hatcheted into 4-6 pieces--nor do I bury wood; other than a few pieces tucked under the coals at the very top layer, I put wood on top.)
In other words, if you control for (or understand) the variables the can affect your cooks and plan (or compensate) for them, you can use water, sand, ceramic, or nothing at all and have very successful cooks.