Much work has been done on segmentation, and more work is required as here is no indication that the company tracks NPS (net promoter score) or changes in SOW (share of wallet). However, once each segment is analysed, key questions can be answered, such as: 1. which sectors should be prioritized and why, 2. what products should be marketing and in what priority, 3. as competition increases, which segments would you protect and how, 4. what initiatives would you put in place to yield short term benefits vs long term benefits, and 5. as you prepare your marketing plan, which plan elements would you be included above what you've already mentioned.
One option is to segment by potential. Given this approach, segment 4 (potential index of 200) would be prioritized. Another approach is to segment by profitability; given this approach, segment 1 followed by segment 3 would be prioritized. Segment 2 average profitabilty per client is higher, but segment 3 has more customers, therefore provides greater profitability.