I know that I'm still a newb here, but I don't like the idea of a 5th power block myself. That would have confused me and caused quite a bit of frustration.
Since a power pin is only one physical pin, why not write code to make the pin VISIBLE in ALL blocks if that pin is currently NOT connected. Then, once the pin is actually connected in ONE block, have the software automatically disable the visibility in all the other blocks.
The only issue is that there are normally at least 2, sometimes 3, physical power pins on parts. One could assign V+ on block 1, V- on block 2, and GND on block 4. I'd suggest that the power pins be connected in all the same block, but if a user has some crazy reason to want it like I just mentioned, I don't see any problem.
As simple, or as difficult, as the user wants to make for themselves!