Bad idea?

In general smokers are airtight low oxygen cookers but there are a few well designed hybrids. The danger in adapting a smoker to a grill is the possibility of inadequate oxygen and the fire going out and the gas combusting with a big boom when the chamber door is opened.( usually there is some smoldering wood which acts as the igniter) If you do it I would not close the chamber door with the gas on.

I just re-read your post and noticed you would cook with the door open. Just be careful you don't have a " helpful friend" close it.