TNT Airways (TAY) will be operating a pax 737 from Brussels this summer to the typical med holiday destinations. This will be flown by a leased 737 (one of the icelandic lot if memory serves) but I couldn't say about FD crewing (CC are TNT provided).
Yes its not core business but after the recent bankruptcies in Belgium the major holiday companies need capacity on the sunshine routes and TNT has an established AOC and already operates the 737 in freight config.
Although not noted TNT has the option to convert future 737 conversions from Pure freight to Quick change. Greater utilization lower overheads spreading the cost and all those good things....