I don't know if there would be much of a demand for a four season Tarptent--especially given the popularity of single-poled tipi tents ala the MegaLight.

But then I thought some more, and decided that a less-expensive alternative to a Warmlite would be worthwhile. Keep the tunnel shape, but have the vestibules be floorless, and make it with doors on each end. Obviously, the double-walled approach used by Warmlite would be required to keep condensation down. The doors should have both mosquito netting and breathable ripstop paneling--the second is needed to keep spindrift out of the interior.

There is one problem with the double-walled approach: how to vent the roof? Perhaps the solution could be similar to what TNF uses in its expedition tents--have zippered panels in the interior ceiling backed by mesh that match with vents with stiffened eyebrows on the outer layer.

Designing a winter tent out of non-breathable materials is a tough challenge--you have to be able to close the thing up tight from wind and spindrift, yet still allow air circulation so that you don't die of asphyxiation.

I'm also not convinced that sil-nyl is suitable for tent floors when camping on snow--I've seen water come through the floor of even the 1500mm coating of a MH Trango 2. It's heavy, but there's a reason why Bibler uses the floor material it does on its top of the line tents.