To have such a large fleet and not one aircraft on "standby"
Is setting yourself up for EU261 compensation however it is due to this mentality that airlines will delay 1 flight by 24 hours rather than delay 4 or 5 flights by 4,5 and 6 hours to recover the program.
In comparison Jet2 try to always have a minimum of 4 to 5 aircraft on standby fully crewed ready to launch at most times of the day, they even have one strategically placed in ALC most of the year to bring delays under the 3 hours, the others are in LBA and MAN their two biggest bases however I don't see why there couldn't be a 321 on standby on MAN or even have it where it does no flight during the day but does an overnight flight that way it will give some slack in the program to recover.