Power and ground planes

 WIth half a question you get half an answer. :)  Nothing wrong with the idea but what about the *rest* of the PCB?  Where are the planes located?  Is this an asymmetric stackup?  How thick are the dielectrics?  What weight copper?  Where are the signals?  Too many unanswered questions to address your initial question....

I'm okay with the rest of the board. pwr-gnd-pwr is something that I haven't done before. Here's the stack-up:

 Are you familiar with "cap" lamination and "core" lamination?  Depending on where you spec core thicknesses you might end up with a higher cost board (core).  Cap lamination uses vacuum applied foil on the outer layers.

You could try altering your stack up a hair like this.  Now signals are etched on core layers which fabricators prefer.  All power plane pairs are on cores.  You could then spec a core material like ZBC2000 or Oak Mitsui if you need buried capacitance.

I would also consider swapping some of the power/gnd layers so that I had a high-speed GND-sig-sig-GND routing available if you need to worry about noise on high-speed pairs... (another topic?)

Thanks redwire. I found a solution.

 Sounds good.  Stackup looks fine.  Did the overall thickess change? :)

Be sure to think about your return current when routing pwr/sig/gnd especially if you have signals going off to a backplane with different return layers.  If no external signals then use caps as signal return AC paths nearby the via.