Oh, I've definitely done this. During the WN fare sales, I'll sometimes snag something as soon as I see it because I know the $49's and $59's can disappear fast. (Sometimes I'm doing this on a competitor who's responding to the WN sale with even less inventory than WN.) Then I'll figure out that evening whether we actually want to do it (it usually involved wife or wife + kids) and, occasionally, cancel it entirely.

So the 1 change or free cancel thing is great. I've just never thought about trying to do a bunch of changes to one ticket. And thanks to this thread, I now know I actually can't do that on Alaska. It's best to just cancel and rebook a new PNR.