Yes segmentation combined with a different service model for each segment can help you best allocate time, assign the right resources and generate more ideal clients.
Having helped many professional service practices through this process, here are a few thoughts.
1- When doing the segmentation create a set of criteria to segment clients based on more than just profitability. For ex. if the client has been a great referral partner resulting in lots of new business even though they are a "B' you might want to treat them like an A. Think about the kind of client you really want- do they agree with your recommendations, open new doors for you, etc.
2- Put together a service model that treats different segments differently. For ex. you may choose to meet with your A clients 4 times a year (as opposed to 2x for a Gold client), return their calls within an hour, invite them to special client appreciation events, and contribute to their favorite philanthropy..
3- Assign work to your staff based on their tenure and expertise. C clients may be ideal to build skills with new employees, A's might be reserved for the partners because of their complexities and potential for high level introductions.
4- Everyone on the team should be aware of the segmentation and the related service model to deliver services as promised. Expectations are everything! If you bring on a C client and tell them you will be meeting with them 2x a year they will be expecting your call to set up those meetings. If you only call once- that is a problem. If C's call you too frequently the potential opportunity cost of your time with A's (who have the potential to bring in more business and refer you to those similar to them) is huge. There are effective ways to deal with those clients too.
Best on driving the right levels of service to the right clients- when you get it right you will grow faster, build a training process and career progression for newer staff and optimize everyone's time.