Hi Chris
I have just read through this entire post, but as far as I can see, no-one has proposed a solution to your problem in plain language. But in short, yes - what you want to do is certainly do-able. I use this method in all of my boats.
You wire the 12V as you would normally, through your fuse(s), isolator switch, and ESC to your motors.
Now, for your radio and servos, regardless of whether or not there is a BEC circuit on your ESC, I use a device known as a UBEC. This takes the 12V from your battery and converts it to 5V (or 6V selectable), and either 3A or 5A depending on which unit you buy. Even if your ESC does have a BEC circuit, use of the UBEC totally eliminates any possible issues due to incorrect connection, or possible internal failure within the ESC. There is no direct connection anywhere between your 12V and 5V systems. (A BEC circuit within an ESC usually has one common connection between the 12V and 5V circuits, making it very easy for an internal failure to occur, which would see 12V applied to you radio and receivers, with spectacular results.)
The 5V from your UBEC is connected directly into either the BATT socket of your receiver (if it has one), or into any spare socket (if it does not have a BATT input socket). Then plug in the RX cables to the ESCs and other servos, and away you go. This method also eliminates the issue of whether or not you need to disconnect one wire from the servo cable to the radio - so you never even need to think about that. It also eliminates any issues arising from language translation. It also eliminates any need for a separate battery for your receiver.
If my ESC or power board does have a BEC circuit, I do not use it for my radios - but I might use it for other functions such as to drive LED lighting.
Des.