A heter based on the fact that something is not nahug is relatively meaningless if we take a positivist view of halakha. But I’ll reserve my Maimonidean impulses for other venues.
Sleeping in the sukkah is something I was zoche to do the first night of sukkot. I had set up an aerobed in the sukkah. The Rema explains, “U’mah shenohagin lehakel achshav beshenah, she ein yeshenim be sukkah rak hamedakdekin bemitzvot; i.e. on his days only those careful about mitzvot slept in the sukkah, presumably due to either a) the Mordechai’s explanation that the extreme cold precludes the practice (Mishum Tzinah, d’yesh tza’ar leyashen
bammekomot hakkarim), since it is uncomfortable to sleep outdoors in the cold, or b) his explanation, that sleeping in a sukkah, unless a private sukkah, prevents husband and wife from sleeping together. This he bases on his understanding of teishvu k’ein taduru, i.e. that yeshiva be sukkah ought to be like one’s year round dwelling. The Gra, to my mind, is correct in stating that this application of teishvu k’ein taduru lacks Talmudic support. The circumstances that the Talmud discusses in terms of what would make a person patur from sleeping in the sukkah don’t seem to support allowing a married man patur.