Work permit question - swapping sponsorship (Toronto)

Hi there,

I'm new to this forum, but hoping someone might be able to help me out.

I am an Aussie in Toronto with my partner and our daughter. My partner was sponsored for his work permit, and I have an open spouse work permit. I was able to get a transfer for my work to the Toronto office.
We've been here 2 years, with the work permit due to expire next year. We'd like to stay for another 2.5 years. Somewhat naively, we assumed we'd be able to apply for another 3 yr extension on the work permit. However, just found out about the 4 yr maximum on a work permit, otherwise need PR. We don't really want to go through the PR process, as we def want to move back.
We thought that maybe we might be able to swap so that my work sponsors me instead, and perhaps that might reset to another 3 yrs. However, I suspect that may not be possible, and the previous work permit would still be counted towards the 4 yr total.
Does anyone know if thats the way it works?
Thanks!
Cara