Not the kind of mission-critical product I think I'd want to personally take responsibility for selling as some kind of black box-ish module at this time given, as you say, the details need to be right.
I think such a design (even just the "code" part) would need more than just my eyes on it to ensure that, and more time testing than I'm willing to commit ATM.
But if you have ideas of what an implementation might look like on the analog side I can post a "code" sketch this month, and people could make closed-source derivatives if they like. Honestly the Greenpak Designer is very straightforward to get a handle on, and as its mixed-signal designs simulate more like SPICE than an FPGA sim.
There are a bunch of overvoltage/reverse polarity protection ICs availabe; most seem geared to automotive applications where the hazards are mainly load dumps and someone connecting the 12 volt battery backwards, relays obviously aren't helpful to defend against the type of over/under voltage conditions caused by load dump transients.