For a BM focused deck I find getting spoils early is a nice way to lead into golds (or platinums in colony games)
The way I think about spoils is by looking at Bandit Camp vs Bazaar.
Identical cards but one gives you +1$, one gives you a spoils.
So as a starting point we could say 2 spoils = $2
I honestly think spoils is worth more than a +1 coin, the main difference between the two cards is that with bazaar the +1 is immediate, with Bandit camp, it makes your deck thicker and you have to draw up the spoils to get the bonus. It depends on the deck, with an engine, especially a weak cantrippy engine, you might not want to get clogged down by spoils, whereas if you had strong drawing or a leaning-towards BM deck the spoils can help break the 5-6 barrier, or jump to 8/9/11 (or multiples thereof if you have a powerful deck)
Opening Pillage is good if the other 5-cost actions are weak (e.g. market) and you want to go BM, so you don't really want the pillage sticking around anyways, since you want to go for gold and never look back. Thing is, I think, 1 Pillage is good, but the more you buy the worse you do, because you could have had duchies or other actions that chain better.
I think, a major breakthrough I had with 1-shots and BM decks is, chances are if you buy an action in a BM deck you will only use it 3-4 times, does the one-shot give you an advantage over that? A breakthrough for me was when I used 2 madmen in 1 turn to get 3 colonies and a province. In that one turn, the game was over, even if it took 4-5 turns for the rest of the colony pile to drain. Yes, they were one shot, but with a one-shot like that, who needs seconds?
In an extreme case for example, if you get 4 on turn 16, and you buy a smithy, chances are it will be a one-shot, as you may only get 1 reshuffle in before the end of the game, is it worth it?