Can you clarify what you mean by "this" not being a good move? Do you mean that passing up might be the wrong move? OR taking the position?
I'm with Jerry on this discussion, I work in the technical side but have worked in my career in Accounting, Engineering, Operations. When I was working for a large vendor corporation, we were the smallest office, but the most profitable competing with the likes of NY, Chicago, Dallas and many more, 95 overall at that time.
Think about this model, less is more. We had less consultants, but more profit on each, less maintenance because of that,(less staff mgmt needed and less expenses) but more responsiveness to our consultants needs (better retention), less clients, but we OWNED that account. I see our service with a client like a virus (in a nice way virus, and because we work with technical people;-), once we get in the door with a hiring manager and deliver the goods, we ask them to sponsor us to someone else either in their dept or some other area that has a need.
If you don't specialize in a controller, contact one of your network people that you trust and do a split with them. Let the client know that you appreciate the opportunity, it's a little out of your wheelhouse, but you're willing to give it a go. That way you've honestly set the stage with the client with minimal skin in the game. If you deliver the candidate they hire, you are the hero and again you establish yourself in another area of that client. Eventually you might hire someone yourself for that market.
I would rather be deep into 3 clients than shallow in 100. That's the model that I saw fail with many of the large vendors. When you walk into the door of your client, wouldn't it be nice if everyone recognized you versus just the department(s) you worked with. I"m not saying to walk away from your vertical but don't turn away business at your door for fear of delivery, it's all in the way you set the stage with your client that sets the expectation overall on the service provided.
Think of it this way, how much time/effort did you put into building that client...once you got in the door, did you look around at your surrounding and say, "I am finally here". I've seen people get into an account, get one job and that was all that department had budgeted for that year. If you spread around the service to other depts, you won't see that problem and you will be very busy during recessions and much busier when it's not. I like looking at my desk and deciding whether I have time to take on another client or to turn them away.
Another thought here - if that client has divisions, you should be like a bee moving from one flower to the next and picking up the honey from the divisions too since you've already established yourself within the umbrella of companies. Ask about their suppliers too, they like working with someone that is working with their clients and everything all connects if you're looking from the outside/in or better yet, the inside/out.
Like Jerry said, "It's what I'm doing"
Feel the fear and do it anyway -- good luck on this Peggy!
Automating the technical side of your business process will let you concentrate on building and maintaining stronger relationships with your clients.
Eliminating information silos and taking a customer centric approach might be something to consider. Our company has developed a couple of customized software solutions that fully automate the recruiting process. The software is based around a Customer Relationship Management model and everything resides under one ecosystem.