I took Jim's advice and added the killall line to the properties in the GNOME panel launchers for all three browsers. A kludge, but an effective one. The "Cafe User" will learn very quickly to open a new browser window without clicking on the launcher again, because the launcher button will crash the app dramatically before starting a new instance.
I'm still thinking about the splash screen idea. I think I could write a tcl wrapper that just threw up a little window with a button that said, "Loading Mozilla, eh?" and give the person some instant feedback on this. Of course, it would be nicer if I could get the lizard logo in there, since it was designed by a good friend of mine (Shepard Fairey, of "Andre the Giant has a Posse" notoriety.) And it would be even nicer if we could include one of those silly animated thermometers that gradually changes color from left to right as the app loads, since the Windoze-trained "Cafe User" loves those little things. Unfortunately, I am not up to the challenge just yet. I'll be working on my quick-and-dirty version in the meantime.