Polymer is still slower than Polymost, even with no lights. That and the draw distance is enough to justify not using it in the DNF mod.
However, if the draw distance was adressed, the maps in the DNF mod could have been made with full-blown Polymer lighting and still have decent performance with creative use of models (for example, if all non-accessible buildings in the first map were made of models). Yeah, it would require a modern system, but the current maps, with all the sector detail, would not even run well on such a system if Polymer lights were added. Not trying to say the mod authors should have done that (because it obviously wasn't their goal); I just try to say that it's definately possible. Models are very, very cheap to render on modern systems.
The Slick Willy map I'm working on, while not stellar in terms of performance, is currently running much better than my new Fusion maps, even though it's actually more detailed and a rather large open space. That's because the desert rocks, for example, are models. If you remember those jungle screenshots I've posted in the past, that's the best looking stuff I've made for Polymer; it runs at 70FPS on my machine. And I think it could be optimized even further.
And if this is possible with an unoptimized renderer, I dream of what could be done if it's ever optimized... yay