My Pixel 7a nearly has this. The “Power” button by default does:
Short Press: Sleep/Wake
Long Press: Assistant
In order to actually get the power menu to pop up, you hold the power button + volume up. You can switch the behavior so that a long press can either be the assistant or the power menu, but otherwise not fully configurable. Feels like that would be an easy win to let us do whatever we want with it.