Thank you all for your helpful answers, even yours Raghu :)

In reply to your questions and comments:
1. We've considered the notion of enclosing the control in a pressure vessel specifically designed to withstand the deep sea pressures. However, in our business, innovation is king, followed only by package size (smaller = better). A pressure vessel would add significantly to the size of the total package. We are replacing existing actuation devices and adding electronics for communications and sensor data. Maintaining something reasonably approximating the original footprint is important.
2. Yes we do have a means to test, basically as Raghu described. We currently have a small vessel that we can fill with fluid and pump up to at least 6000psi. We also have the capability to easily fabricate a container that can go to higher pressures. Consider a hydraulic cylinder designed for such pressures. A simple modification turns it into a test chamber.
3. I share the concerns regarding survival of potted components. However, this is exactly what some manufacturers of subsea products are currently and successfully doing. We are just trying to understand all of the issues involved and benefit from lessons learned. I'm sure component selection factors in and most certainly the selection of the potting compound is critical.

Additional comments are very welcome.
Best regards and many thanks to all.
Steve C.