Capacitive touch sensor on a dense 4 layer pcb

[exapod]

Hi,
In a project i'm designing i have a pcb in an ABS case 45x45x20mmm with 3mm tick walls and because the case is water proof i have to use two capacitive touch sensor on the top side as user interface.
I've never implemented a touch interface and after reading some docs i have some doubt.
My pcb is 4 layer and i was thinking of using separate ICs to read the sensors.
The doubts that i have are:

1) what pcb stack-up should i use? 
    a doc by microchip suggests:
    • Layer 1 (top): Capacitive sensor pads.
    • Layer 2: Capacitive sensor traces.
    • Layer 3: GND plane, except under capacitive
      sensor pads. Every effort should be made to keep
      this ground plane contiguous. This is especially
      true for the area under the capacitive sensing
      controller.
    • Layer 4 (bottom): All components, any LED signal
       traces, power traces, and communication traces.

All the breakout boards that i have seen have an hatched ground under the sensors, example: http://www.adafruit.com/products/1375 .
I was thinking this stack up:

    • Layer 1 (top): Capacitive sensor pads.
    • Layer 2: GND plane, hatched under the sensor pads
    • Layer 3: Power traces
    • Layer 4 (bottom): All components, signal traces and the sensors IC that like the breakout that i linked
       are very close to the via connected to the sensor pads.

2) For space constraint i have to put other traces and components (ideally only the sensors IC) on layer 4 under the sensors. Is this a "deal breaker"?

Sorry for the long topic and bad english.
Thanks for the help.