What do you mean by using hardwood? Hardwood lump charcoal??? You can certainly use lump charcoal in the WSM. You can also use briquettes. Both are used in abundance by people on this forum. Not sure why using briquettes makes no sense to you, but if you prefer to use lump, you can with no problems.
If by using hardwood, you mean using wood - like a log burner does, no, you cannot do that in a WSM. If you really like to work, you can start a fire and produce coals that you could shovel in your WSM but I don't know why anyone would want to do that.