UWaterloo is generally pretty receptive to 8 month coop terms. It's not too difficult to arrange. In programs with one stream however (SoftEng was one stream while I was there), it's more difficult because you essentially end up having to join the next year's class.
Yes. I'm in CS class of 2017. We have 4 streams, so basically everyone is everywhere all the time. You can do whatever you want whenever you want.
Halfway through my first co-op term, I was asked to stay another four months. I was able to say "yes" on the spot. It only took about 20 minutes of work to arrange it with UW. I just had to fill out a form and email it to the right co-op advisor.
