It would be good to have lines drawn between the bases that attract each other in the target mode. The 5 most strong future bonds would be enough. I expect this will provide visual feedback. However the question is if it will be helpful or just overkill?
when you change the bases the strength between the bonds can change, distorting the target in the process. I perceive the bonds in that particular distorted grouping as future bonds. Look at it as potential bonds when suggesting to change the base. Of those potential bonds a selecton of the strongest could be displayed.