The problem is that folks become selfish and it's human nature not to give for the common good.Part time can work if all agree, however, it can also be a management nightmare with keeping people current, fixed overheads, holiday pay, LPCs etc, and usually guys get called in off standby to work, which again can cost money. Job share works better, but with the size of fleet you talk about I doubt it is feasible. 75% roster for 80% of the pay may work, why? because they can actually work you 85% of the normal FTLs on a 75% roster because of how the days off can be placed to keep it legal. No recency issues and max flex for crewing. It really depends if they want a simple formula or complex duty hour/pay related one.. best keep it simple and the bean counters understand. Or offer to let them hire your spare crew to another airline..its been done before.. depends if people want to be displaced.