Not trying to be emotive, I'm just saying that a 'job share' in our business is not as simple as may first be apparent, so if you are trying to sell an idea to the company its worth considering all the issues above.
My wife does a job share in a very senior position in her profession and it works very well, so I'm certainly an advocate of flexible working. However splitting a monday - friday office role in half is a different kettle of fish to splitting a pilot in half.
I suspect, however, that the current climate will open peoples eyes to the benefits of such working practices, itprevents people being put on the scrapheap, and as you say it gives the employer a 'rapid response' ability to spin up, Whilst everyone else is trying to recruit, you can just turn all the part timers back to full time!