A school can apply for an exemption to the rule, I've only heard of the state allowing a student athlete to play Varsity competition without sitting out and that was a situation where a student lived in a district but closer to another high school, his family moved within the district and the family decided to send the kids to the district which they lived in. This was not a move for athletic gain. I don't think that this would apply in this situation.
Now if Drew got kicked out of Regina and was forced to attend West (someone said they already live in West boundaries). Then I believe he would be able to play right away as he did not choose to leave the school.
Or he could go enroll in a school out of state then come back, he would be able to play at West right away.
Of course do we even know that Cook is even interested in the West job?