Love this! I've always wanted to do kalua on the Weber. Great cook, let us know what you thought of it!
I've used this method most of the time and it has always turned out great. The key is to use a mild wood and don't over smoke it. Depending on the size, i usually smoke it for 2-4 hours until it turn golden brown and has a slight crust before wrapping and placing it in the dutch oven. Once wrapped with banana leaves, the smoke flavor will penetrate throughout the meat. The banana leaves will also impart a nutty/aromatic flavor to the meat. Also keep the rub simple with just salt n pepper. If you want to use garlic or onion etc, don't use a powder form in the rub. Instead just add garlic cloves or onion sliced in half when you wrap the meat with the leaves.
For this cook, a leaner meat was requested so i used boneless pork shoulder and removed some of the excess fats. Since it's a leaner meat, i added 2 cups of unsalted chicken stock in the dutch oven.
Typically a bone-in/skin on is preferred as it yields a more tender and juicer meat.