I've though of an idea, actually a fourth option in the "Upload and Deploy Extension"-window .
In the field "Deploy to", currently you can choose: Current version, Next minor version, Next major version.
The new fourth option could be "Next available update window".
With this option it would be possible to roll out a new PTE, without annoying anyone - you can simply say, "from tomorrow it'll be ready on your environment". You don't have to "waste" time coordinating (this can be timeconsuming).
I haven't seen any suggestions about this anywhere else, but I'm sure it would be VERY useful, and probably easy for MS to implement.
Yammer thread link: https://www.yammer.com/dynamicsnavdev/threads/2279407948374016