GFCI and contactor combination panel

The wiring diagram of the following spa panel:

has some wiring missing. I presume the GFCI module in the upper right is one of the modified high current units such as the Leviton

8895 as pictured here:

The big question I have, which the missing wiring might have shown is whether this unit (or extrapolate the question to any such unit) operates by leaving the contactor coil energized all the time and interrupts it when there is a ground fault, or if it is energized to break the circuit? I would think it would be the former, as that would provide a "better safe than sorry" condition if something in the coil loop fails. I'll assume de-energize to open at this point.

BTW, this diagram does show that the neutral really is interrupted. So this looks like what will satisfy my desire as indicated in that big "just how dangerous is the neutral wire?" thread.

Setting aside UL listing of GFCI/contactor combinations, what would be an appropriate contactor type for making my own GFCI panel like this? I'm interested in just how much power that contactor uses. I might build such a unit with an on/off switch to reduce the power waste (in addition to the pull-out disconnect for servicing safety). The on/off switch would only disconnect the hot wires, letting the contactor then disconnect all current conductors (presumably wired in de-energize to open).

And alternative for lower current circuits (15 or 20 amps) that I am thinking of is to just use an ordinary GFCI breaker to feed and protect the circuit, and add a contactor (energized to close) after that breaker to switch the neutral (and other conductors, too). The GFCI breaker (which does not switch the neutral) would provide protection compliant with code. Then the contactor would add more protection (as long as it can open the neutral in compliance with code) by being energized from the circuit itself. So if the GFCI trips (it has to be sensing neutral current to work right), it cuts the hot wire(s), resulting in the contactor being de-energized, and thus disconnecting the neutral as well.