A far better way to have some extra time off without falling for this Unpaid Leave scheme whereby if you take 2 months Unpaid you lose another 1 weeks paid leave for your participation, is to utilize the PROFFERING system in your Rostering practices agreement, and the interface is already on crew direct.
A typical roster would be 80-84 hours on average therefore in theory a Captain can proffer all of his flying at a cost of $80-84K. An F/O could proffer all his roster at a cost of $40-44 k and an S/O for a cost of $24-25,200. All ranks would have a fair amount of salary still remaining (zero salary with unpaid leave!) with no pro rata costs in the company favour and full entitlements intact.
Proffering trips before and after leave and days off can generate very acceptable amounts of days off at reasonable cost. The system needs to have givers and takers to work and if we all took unpaid leave obviously we would shoot ourselves in the foot because we would all be on minimum G days and proffers would not be awarded.