I have some destroyed trader POIs in my modlet. You can take any map and (before using the map) with some quick editing replace traders with those alternative POIs. But I see now you want traders, just not missions. (Your msg rolled in while I was typing.) I don't have an answer for that.
Yah, I used to think the traders were dumb, but there's nothing else to do with all the garbage loot. Otherwise it's just gonna build up to infinity. All I really want is to get rid of the missions, because the last time I tried making a server the carebears just grinded missions all day everyday. It was the most efficient fastest way to level up and get loot, but it ruins the game because nobody wants to explore or build or interact.
Nothing wrong with not wanting quests. Still, I don't think there's any reason to try to force people to play the game the way you think they should play it. If people enjoy quests, why not let them do quests? Lots of people quest AND build AND explore. If people don't want to build or explore, then removing quests will just make it so they go to a different server where they can play the game the way they want to play it. Just my opinion, of course.
As far as a wasteland only map, RWG doesn't let you do that anymore. But you can just edit the biomes.png file after making the map (before you start a new save on that map) and paint it all using the wasteland color. Make sure you use the exact color. You can use the Eyedropper tool from any image editor to copy the exact color and then use the Fill tool to fill everything with that color. Save it and then start a new save with that map and it will all be wasteland. HOWEVER, once 2.0 is released, if you start in the wasteland, you will die unless you disable biome hazards.
I don't recommend generating a map with little or none of the other biomes since it can mess up the map generation.
It's always better to generate a well distributed map and then edit the biomes.png as it was suggested before.
If you want all wasteland, it's as simple as grabbing the bucket tool and filling all with the same orange
As Riamus said, no point removing that. Each person has his own way to play, many love it but they will leave your server quick when they see no trader quests.
Maybe look if you can lower the XP given for trader quest.