Include a snooze option so that if the user is at a very productive point, they can extend the timer just by a single keypress.

I don't think that's a very good idea since the system itself and a doesn't encourage changing the length of the time. Here's one good explanation.
source: http://getitdone.quickanddirtytips.com/how-to-overcome-procrastination.aspx

"Tip #2: Stop When the Time is Up, Even If It's Mid-Task

Once you're off and running, it's tempting to hear the buzzer and think, "I'm doing so well I can just keep going." Don't! Your brain let you start this project because you promised you would limit yourself to 15 minutes. If you cheat, your brain won't be able to trust you next time. So no matter how strongly you want to keep scraping your black grout fuzz, stop, clean up, and finish your 15 minutes.

It's actually better if you stop in the middle of the task. If you reach a breaking point, your brain can procrastinate more easily in the future. After all, that's what a breaking point is. But if you stop mid-task, your brain will want to jump back in tomorrow to continue the process."

I must say I think this is a really bad idea. It completely undermines the idea of the Pomodoro technique entirely, as to have proper results from the technique, you really have to trust it and follow it quite strictly. I do hope (now that this idea has been scheduled) that it remains an optional extra.

I agree that the point of the Pomodoro Technique is that a Pomodoro is indivisible. A snooze button makes the concept blurry and makes it more customizable in a way that prevents it from being the Pomodoro technique.

I wouldn't add this feature, OR make this feature be toggled as a visual GUI. I wouldn't want to see this unless I chose to