the FR flights come in after all the based A/C have left,
Excellent point. and maybe part of the Airport management team strategy - Other airlines such as EK, Vueling, SAS, KLM, AF, Non-based charters etc... bring valuable business, which keeps the airport busy long after early morning based a/c have departed.
It'd Probably be difficult to accommodate many more o/night based a/c wanting a 6-7am departure for a full day utilisation of eqpt.