The spite sounds fun, but giving the customer what they ask for when they want a shit job is still going to reflect badly on you. A lot of the time, potentially problematic customers should just be directed elsewhere to make their data someone else's problem.

Whether or not you gave them exactly what they asked for, if they don't have a realistic vision/hardware/site you're setting them up for a bad time, and they'll bitch about you because you couldn't translate the ephemeral concept of an idea that never left their skull into something that looked good or they wanted, and they'll be sure to tell everyone who made the mess they're unhappy with.