The question was (and in some sense, still is) vaguely worded. I had interpreted it as something more complicated (and arguably much more interesting) than it really was. As a result, I posted a partial answer, explaining what some of the difficulties are, and asking for much more details in the specific situation that the OP was interested in.
In the end, though, it seems that the OP was actually asking something else, at least I think so. Perhaps not.
My question, however, is this: if one posts a (partial) answer to a question, and then discovers that the question was really asking something else, should one delete said answer, or leave it there for other users' interest?
In this particular case, I will nevertheless wait for it to become clear if, as I suspect, I was really (partially) answering a different question.
I would probably edit in, at the top of the answer, "On reflection, this answer is not quite what the OP wanted. I am leaving it here for independent interest and for contrast" or some such. This may prevent people downvoting without understanding what is going on.
P.S. the question you answered is nonsense, and the OP unresponsive. I might well delete my answer for such a thing.