This is a very specific scenario, I do not want to expand it to anything other than the parameters I specified.
You made an incorrect assumption - I never said I needed to fully "control" the latch (i.e I dont need to do both operations). I only said that I needed to "unlatch" it. If the switch, when triggered, delivers the correct polarity of current to the latch (assuming the circuit is complete) - then it will in fact unlatch it, correct? So I believe you can do that with a SPDT switch right? Because all you need to do is apply the current and the latch will perform as it is designed.
I realize I may not *need* latching relays, but if it vastly simplifies the system then Im willing to use them, as they dont seem to be prohibitively expensive.