I think downtube shifters make sense on a touring bike. The front mech works better as a friction shift when using with a triple because it can be trimmed easily, and otherwise triples are notoriously difficult to keep in perfect tune. Since we are not talking about racing here, the downtube location for rear shifting is not a problem. It's not like you are going get dropped because you missed a shift. As far as the safety issue, ok just don't shift when you are in traffic. Your legs can handle a cadence of plus or minus 10 rpm for 15 seconds without any real drawbacks.
Bar-end shifters, already widely used on touring bikes, require longer cables and I think the cables are also slightly harder to change out should they require replacing on tour. So sure, DT shifters would be very nice on a touring bike, imo. Some, such as myself, would prefer that solution to bar-end shifters.