I've had a M-B based Sunseeker with the Trekker cap, as they call it, that deletes the bunk. Unfortunately any pictures of mine wouldn't be comparable as Dynamax does their storage and TV mount location differently Sunseeker.
But I can try to answer a couple of your questions.
Would I chose to go with a Trekker again? Definitely YES!. We just bought a new Sunseeker and it has the Trekker. Every motorhome we have owned except one has had the Trekker cap. This last round I had to do a "special order" to get a Trekker on our particular model.
Any MPG improvement? I don't know. That would be hard to document without side by side testing. At one time Forest River said the shorter cap gained about .5MPG.
It does gain you a chunk of Cargo Capacity losing the weight of the overhead bunk system. Someone from Dynamax should be able to tell you how much of a gain you'll see.
Another big improvement is you'll lose the lifting wing effect when trucks pass. The standard cap acts as a wing and you'll feel a truck pass. The Trekker minimizes it. And the view out the windshield without the bunk is great.
Does it impact resale value? I have not had any issues with resale / trade in value because of the Trekker. You do basically make the coach in to a two person coach...especially if you also replace the dinette with recliners. But their is nice market for those units.
I hope this answers some of your questions. Since I discussed the Trekker I'll sneak a picture of our new Sunseeker with the E-350 / E-450 series Trekker.