I think this would be a great idea. I've only seen iMindMap's promotional video on this feature, but this displays one important aspect which would make a major contribution to its success: the ability to use the equivalent of MindManager boundaries to create radial slices to shade each branch group, which apparently can be resized regardless of the number of subtopics in each slice.
It this is possible it means the map can also function as a true pie chart. In the video the slices appeared to be being resized manually, which is great, but what would also be even more useful would be to add the ability to resize them automatically, based on parameters such as duration involved or effort required. So for example if you had a radial map with three branches, one with a total duration of 40 days and the other two with 20 days each, the first would automatically form a slice taking up half the map. Ideally the sub-branches would behave in a similar fashion.