Japan’s Softbank, and its maverick chairman Masayoshi Son, has been interested in adding a US cableco to its growing wireless empire for some time, either to combine with its existing US subsidiary, Sprint, or to replace it. There have been various reports over the past year, of talks with major cable operators as well as T-Mobile USA and Dish Network. Now, the reports are concentrated on a possible $100 billion bid for the second largest cableco, Charter. The issue here is that the only way a merger between Charter and Sprint can prosper, is if current Charter CEO Tom Rutledge is put in charge. The aim, it seems, would be to create a fixed/mobile giant to compete with Verizon and…