You can get two kinds of crosstalk for signals that are within several dielectric thicknesses of each other: forward and reverse crosstalk. The signal integrity tools are wonderful if you have signals where crosstalk is critical our edges outrageous. If the signals are further apart or the edge rates are low, the crosstalk tends to be minimal.
PC board manufacture might affect your choice. I understand it's less desirable to have the ground/power planes asymmetric for handling the board-stack as it's pieced together. Talk to your PC fab house.
I'm a fan of good grounds but it's hard to avoid overkill. We had a board that was S-G-P-G-S-S-G-P-G-S. The board only sported four signal layers but they were all referenced to ground! I think this was a prototype stackup that made it into production.
If I had my own board to do again at my own risk - no other engineers to review the work - I think I'd go with S-G-S-S-G-S but use power pours (with appropriate filtering) in one signal plane and/or one ground plane only in an island around the chip. With bypassing that's appropriate to a ferrite-isolated island, the power-surge jostling of the ground plane is reduced. The signals are all referenced to ground outside the island with appropriate decoupling at the edge of the chip to keep return current paths short, keeping EMI in check.
With power pours, the power can be routed on signal layers through lines sized to carry the raw current without a significant voltage drop or temperature rise. The ferrite isolation keeps these power distribution routes from causing problems with nearby signals by reducing the edge rates for surges that get past local decoupling.
You may consider beefing up your grounding scheme only in the region where the analog circuitry is critical and go with a more standard S-G-S-S-P-S stackup where the power and ground planes are well bypassed, especially where signals switch layers (for that "ever popular" return current path thing).
I like to keep my signal impedances to a specific design level, balancing the dielectric thicknesses to give me the impedances based on my routing rules for internal/external signals.
There are so many ways to come up with an acceptable board that I wouldn't lose sleep over finding the "right" stackup. Just make sure your PC board fab thinks the stackup sounds good.
- John_H