I would propose 3 terrain features that need improved/different treatment in the DTO context.
Hills. There are NO hills in current DTO! We have hillocks and Escarpment. Bd 25 is a mess. Algeria, western Tunisia is all hills, regular old hills with scrub and crags. And there are plenty of regular, bald hills in Libya/Eastern Tunisia. I played WCM 2 Scotch on the Rocks which uses bd 3 with SSRs changing all woods to crag so that you have a barren hill with lots of crag - very nice desert feel and a real hill mass w/out the Bd 25 craziness. Maybe the Korean War hills will help support better desert hills, but need some boards or overlays with "normal" hills for desert.
Streams/wadis with vegetation. Go to any arid part of the world and the vegetation is concentrated around streams -duh! But in ASL all the stream and wadi overlays are devoid of plant life. So some boards/overlays with these features would be good, could include some Valleys too, little "flood plains", to break up the monotony of the blank boards, provide phase lines and objectives, cover etc
Desert villages. We have individual desert building overlays, but no villages/cities. Must have been some fighting in such terrain. Lots of narrow streets, low buildings, could do desert colors.
All of these features could also be used for non-DTO theatres, Crete, southern Italy, Greece.
I agree with others in this thread that something "different" and "special" needs to be done with DTO IOT raise interest. The current approach is obviously not working and of course, the core module has to be reprinted. And that is a shame because there is a lot of rich history only lightly covered currently in ASL.
FWIW, I have no problem with the overlay approach and it does make sense for DTO. Would love to see bigger, more complex overlays that work with the "Fort" boards used more and DTO would be a good place to experiment with that.