The AF "needs" you. I'm of the belief that the AF can be told to wait.
While on Active Duty, each of us... and our families... were often managed in a crisis manner of "we need you to deploy NOW!" Many things seemed to be an emergency because of lack of planning. As an AD pilot, we didn't have a choice.
Now that a pilot has left active duty and has an airline job along with their Guard/Reserve job, it's time to tell the AF they will have to wait. And 6 months is not unreasonable. The AF will not crumble because you cannot meet their timeline.
Giving up union protection by remaining on probation is probably not going to be a factor. But... what if it is? Will the AF rescue you because you went on mil leave 6 months before your probationary period was up to help the AF out? How's your family going to feel about your gamble if you lose?
Most of you have SGLI, right? Why? It's because it is very cheap insurance.
Waiting a few months and getting off probation before diving back into the squadron is ALSO cheap insurance.