Well to take a step back and evaluate the question of "who needs ds" - most answers to typical problems come down to using a hash table or an array... or some trickery of both. So... I can see this question as being useful.
I am afraid that I am missing the point of why YOU chose this approach if you can't answer this question. No offense to you. It seems like you came from the approach that if people want this job they will do this thing. Seems noble and with good intentions.
But DS is much more than that. It is the basics. The definition. The building blocks. Lots of reasons why you would want to ask about it.
I've actually been asked something similar prior to working at IBM. My caveat was that this question was asked in the interview without any preparation.
However, I can see how some people would find this challenging. It may seem like a lot of work for some people. Especially if you worked with some engineers that freak out when such a task is presented. If they don't have an outline, a set criteria, the protocols, previous samples, and the such. then you will have a bad time. Such people approach problems very systematically. As long as your task is clearly defined and has such things, then it should be easier in theory.
The people who aren't phased then won't be phased. The people that may see this as challenging shouldn't also be phased. Finally, considering monetary incentives for such additional work could smooth out some issues. You could pose such things as an investment and a risk mitigation strategy to your elders.
Anywho, these are some thoughts.