Acutally, the situation is not that straightforward: it depends on whether the condition is time-bound or perpetual.
TIME-BOUND EXAMPLES
If I had the money, I would take a vacation to some place warm this coming winter.
If I had had the money at the time, I would have gone to Tahiti before I got married and we had kids.
INNATE "PERPETUAL" CONDITION EXAMPLES
If he had a brain, he would sell that car and buy something reliable.
If he had a brain, he would not have bought that car in the first place.
It is not truly idiomatic to say "If he had had a brain..." although it is grammatical.
Your example is tricky in that it is an either/or condition, one of which is a time-bound condition, "the blueprint", the other, "a brain", a perpetual condition. It's a bad question in that regard.
P.S. Further on the "innate" qualities. To my AmE, they call for an irrealis construction with were. If you had not been so pale-skinned, you wouldn't have gotten such a bad sunburn. That sounds unidiomatic to me, though I recognize it as grammatical; I'd want to use were there: If you weren't so pale-skinned, you wouldn't have gotten such a bad sunburn. Same with If I'd been you, I wouldn't have bought that car. The tense had been sounds wooden and I'd use were there.