easyJet has made some red eye flights work. I flew a night Athens flight for 3 years, departing LTN 2230 and returning 0830 the next morning. The loads were always very good. The return leg left ATH at 0600 local time, which was a morning departure for the passengers, even though it felt like the middle of the night for the crew.
As mentioned, if we returned late, the next mornings first wave depature was affected. Also, it was very unpopular with most of the crew. Most importantly, it was a very inefficient use of crew, as it took up two days duty to operate 2 sectors, as you were requirred to take a lot of rest under the FTL rules afterwards. Crew are too valuable a resource too spare for red eye flights at easyJet, especially after this summer.