Just stating the obvious, but perhaps not so to the outsiders of the profession.
Flying pure EASA FTL to all of its limits is fraught with danger. They have been designed after much industrial struggle, to allow for various and vastly different operational models. Short-haul jet, regional turboprop, WW longrange, night freight, et al. The FTL "envelope" in its individual corners enables some unusually looking things, such as 11:30 stick time a day for a two man crew.
To keep the duty load reasonable (safely non tiring) one cannot venture from one extreme point of the FTL to another, and then another and then all of them. That would not work, fatigue is sure to appear - and hence the requirement for Fatigue Management System.
A group of pilots sharing the same operational mode can be pushed quite hard to the limits in one area for the mutual benefit of their employer's economical longevity - and safely so - as long as they are not made to hit the redlines of all the limits (that had been drawn to allow for another type of flying work).
It could be a very robust Fatigue Report system, national regulation or in-house industrial agreements that assure the pilots are only made to play one "role". Typically an airline would have only one of those three since in peaceful times one is sufficient. Lift the restrictions, stretch people far and wide, and it is heading towards a sorry state.
I understand in the UK the old rules did not allow near as much as the EASA FTL. But it was never ment to be applied in its full extent to one (group of) individual(s). Godspeed.