Make a file called "server.cs", put this in it:
function servercmdUpdateMods(%c)
{
if(!%c.isSuperAdmin)
return;
setModPaths(getModPaths());
messageClient(%c,'','\c2Mods have been updated.');
}
You'll need to package that as a Script_Something.zip (with a description.txt) and then tick it in the Add-Ons menu. I'm not sure what this will accomplish though, setModPaths(); will only refresh the resource manager (to detect files that have been deleted/added) and won't disable add-ons on your server or include ones you just installed. All the uiname lists are cached and then sent to the client along with the datablocks so you'd need to re-send all those too which would result in a bit of server lag.