Due to the geometric constraints of my intended application for the NHS3152, it isn't possible for me to access the VSS pins/pads directly to provide a return path for the decoupling caps connected to GPIO3 and 7. I also want to keep GPIO10 and 11 accessible for SWD. In light of this, I was thinking of shorting the unused ANA05 to ground (I can fabricate a custom HVQFN footprint by copper etching) and connecting the ground side of the capacitor to ANA05 through a 10k protection resistor.
Would this be a sound plan? I cannot use any of the other GPIO pins set to low since they wouldn't be accessible in the final form factor of this application. The role the IC performs in this setup are simple I2D measurements on the analog pins A0 (for instance) and A4. The decoupling cap is in place to allow the board to function over NFC.
I'm not aware of any adverse adverse effect when doing this. You can route VSS to an unused ANA pin. Do make sure it is unused!
Note: I don't understand the use of the cap. This may as well be removed.