Even if this is a Global *Week* of Action, I think that the global aspect is more important. So, we should let people who cannot organize actions during that period because of exams the possibility to organize something after that period.
For the symbolic aspect : even if a week consists of 7 days, 12 is the number of figures on a clock, so we can consider the whole week as a clock, and even represent it concretely : we can build a big folder clock, and put it in a place where a lot of people can see it, and at the end of each day (the whole world at the exact same time), we can move the hand to the next number, so that everywhere, everyone has the same "Clock of Action". Thus, people who don't have actions to do anymore can still think about those who do organize some actions. Well, I don't know if I made it clear. Anyway, that was just an idea to make the 12 days more symbolic...In case we need to make the Week a 12-days "week".
But if people don't want to extend the GWA till Friday, groups who cannot organize actions during the week can perhaps try and do the most on November, the 5th...

As I've already mentioned on the chat there is one problem concerning the whole concept of a week of action - the intensity. I think that the time frame (regardless of how long it will be in the end) should just be cramped with creative actions so that it doesn't become a 'week during which there are few actions'. Judging from my experiences with the german educational strike, this means an incredible amount of work that increases with every day we add to that week.
So unless your concept of the GWA is a more open one we should bear the workload (isn't that one of those funny Bologna words?) in mind in order to make it a successful week. I don't know much about the last GWA as ironically I joined the struggle because nothing was happening at my university..
Otherwise I see no problems in the extension.

Regards.
Flo