I also understand that the “poach police” may intentionally/inadvertently kill innocents with their blanket immunity;

Is there any evidence that that has been happening? (This article is from 2017, and it mentions "more than 20" poachers being killed in 2015, but doesn't mention any non-poachers being killed, which it seems it would have, given it's talking about the downsides.)

While I agree that taking the fight to the people financing the poaching, reducing the number of poachers - and providing a very clear disincentive for other "poor af" hired-guns to take up the mantle - could still help.

Personally, I don't think any implied sanctity of human life extends to people who are killing endangered animals for profit.