Very neat! Only suggestion is perhaps a CToP variant of the timer, Bye Bye There! And all. Instead of summoning pizzaface when the timer winds down, putting your computer right to sleep if DreamTime is on.
A CToP variant is something that I've been thinking on implementing in a future update, because it's really simple to implement actually, just some tweaks and it's done, so it should be released on the v1.3.
And yes, instead of spawning PizzaFace, it would directly do the action that's supposed to do (DreamTime, Deep Sleeper or Custom Command) like you said, so you can actually make a timer to shut down your computer more easily.
The only thing that I'm not sure how to implement (or if I'm gonna implement at all) is the Bye Bye There! OST, because of how to implement the loop of the song, mainly because the length of the timer can be 3 minutes long, or 4 hours long, the lap 2 and 3, and so on, so maybe It'll just play regular It's Pizza Time!, The Death That I Deservioli, and such.