Most grills won't appraoach the temps of a BGE or other ceramic cookers which can hit 1,000 degrees with ease. The BGE like a tandoori is made from ceramic so you have some moisture retention as well. I use a combination of the plate setter and a pizza stone so it's more indirect but not all that different from a Tandoori as I can invert the plate setter and get the stone very close to the fire. I'd say a little smoke and high temps are key to replicating a Tondoori. I've never tried it but I would suspect with a little ingenuity and some lump charcoal you could rig up a WSM to work very well.
I think the most wonderful thing in the world is another chef. I'm always excited about learning new things about food. Paul Prudhomme
I'd forgot how hot they get. If you already have one, it would be a waste not to tandoori with it, wouldn't it? And another argument for making the choice of a BGE, Primo, or similar if you're buying an outdoor grill.