The most important mods you can make, in my opinion (backed by 4 summers of cooking on a Gourmet) are:
1. Install a charcoal grate so the ashes won't build up and smother the fire. I think this would be much better than the wholesale surgery you've suggested.
2. Create a way to control the airflow into the hole on the bottom of the smoker. This is the only way you will have control over the cooking temperature.
3. Install a real thermometer. The easiest and cheapest way is to drill a hole just below the top cooking grate, and insert a 6" candy/deep fry thermometer.
Once you have done this, you will (1) have a way to control the temperature, (2) have a way to know - accurately - what the temperature is, and (3) be able to have the smoker cook for several hours without a lot of attention.
You still may have to dump the ashes in the middle of a long cook, and load additional charcoal. Using lump instead of briquettes would help with that problem.