Remember
It a nice idea, but it's fundamentally flawed because it assumes that an exactly 50/50 split of men and women are applying for those jobs, it also doesn't account for any statistical variation.
To reverse the scenario in order to illustrate my point, let's consider midwifery. Men are grossly underrepresented in that field (something like 90% plus midwives are women)
What if we implemented your plan?
For arguments sake, let's say there are 100 midwife jobs to fill, so we should split them down 50/50 between men and women? Right?
But what if 1000 woman have trained to become midwives, and only 50 men have? Every woman has a 1 in 20 chance of getting a job, it's incredibly competitive and difficult. Meanwhile every single man who applies gets the job. If you were number 51 on the female list, how fair would that be?
Obviously my figures are made up for ease of illustration but they make my point.
Having a rule that says all jobs must be filled by an exact ratio of 50/50 men and women seems fair at first glance, but is actually incredibly unfair and inefficient.