And the bigger point is, the Wealth system is supposed to be a fast, easy, and dice-interactive method for doing something that is very complex (track modern finances in the age of investments, credit, direct-deposit, and trust funds) ... not a system of "perfect realism".
It's akin to hit-points. One can say: "What happens in D&D when somebody gets their arm cut off at the elbow? Is that like, 10 hit points or do you say 20% of their hit-points?" Hit points doesn't really WORK that way. Doesn't mean they don't work, but you can't say: "I cut off his leg at the knee, so, he should lose 25% of his hit points and not be able to move, right?" That breaks the system. People really can get their leg cut off, and it really would hamper their movement, but allowing people to say: "Oh, I cut off his leg." unbalances things.
Same with: "Oh, I'm going to die, so I spend everything I have." In a game of high action, that might happen every week. "We're going to assault Count Raab in his high-mountain estate. Suicide. I go nuts and buy a tank. I'll worry about the consequences if I survive."
Knocking your Wealth down to +0 can mean anything you want "in story" and can be reached a number of ways ... buying many purchases only slightly above your means or taking 20 on a huge purchase. Maybe you take out lots of loans, or cash in your stock, or cash-advance your credit cards.
It's like you have 15 hit points and the GM says: "The Orc hits you for 15 hit points." You can say that the orc slashed you across the chest, or struck a mighty blow to your head, or stabbed you with his sword center-mass. And it's good to say those things. But, essentially, they're story that you build to explain what has already happened in the rules.
So, I wouldn't tweak the rules. If somebody wanted to go crazy and blow their wad in preparation for Count Raab, they can go ahead and roll for the items and spend themselves down to +0. Even somebody with +1 can take 20 and get something PDC 21.
--fje