For most managers, one level of indirection higher.
"Is X possible?", "I like it, but are there any other possibilities?", "That sounds fun, but have we looked to see if there are any available tools that we could leverage", etc.
These are all the types of questions you'd expect a clueful manager to ask the people under him, but they actually work pretty well to guide a superior who thinks they have an answer, but you know it to be the wrong answer. They have to arrive at the new answer themselves, and implying that there is a better answer (such as 'did you know that a tool exists and does all the stuff you are planning') will cause them to be defensive. Let them work their way to the solution themselves, though, and they'll sing its praises for you.
