I like your idea of using a kettle. I'd keep the middle section on the WSM, though. The access door provides a pretty convenient way to affix the tube as shown in the link Doug included.
The only problem with using the kettle is there is no logical place to affix the tubing. The only thing I can think of is if you tape and secure it over the top vent (fully open). Then you'd have to switch the kettle to being the smoke source, and the WSM to being the food location. The only other problem, however, is getting enough airflow through the tubing into the chamber where the food is. I see two ways to do this. First, is by using height. If you can somehow set the WSM significantly above the kettle (like having the WSM on the deck directly above the kettle) so the tube basically runs nearly straight up into the WSM, that would probably work. The only other option is to use a fan, like shown in Doug's link. Otherwise, I think you'll lose most of the smoke through the bottom vents or under the lid of the kettle, rather than getting it into the WSM.
Hope that helps spawn some thoughts... Good luck and please let us know how it turns out!
