Interesting post Jonathan. I think the idea of proactive complementarity goes into the right direction, but there are also some dangers in trying to rush domestic prosecutions. The International Crimes Division (ICD) of the Ugandan High Court would be a good example for the type of domestic prosecutions furthered by the ICC that you suggest. The Court was set up in the scope of the accountability discussions during the Juba negotiations with the Lord's Resistance Army. The need to talk about accountability arose due to the fact that the ICC had issued warrants against LRA commanders. In the process of setting up the ICD, judges flew to the Hague for trainings and the Office of the Prosecutor shared information with the Ugandan Directorate for Public Prosecutions. Without going into too much details, the ICD has had a bumpy start. It has tried to indict a mid-level LRA Commander, Thomas Kwoyelo, based on breaches of the Geneva Conventions and national Ugandan law. During the process it became clear that the court had huge problems to guarantee witness protection. There were issues concerning the fairness of the trial due to some problems in sharing evidence with the defence. Additionally, sources close to the ICD claim that the court lacks the proper procedures and experience to judge cases of this magnitude.
Some people I have talked to have suggested that the ICC is just supporting domestic prosecutions, without caring for the quality of the processes. The problems of the ICD serve critics of the ICC as just another proof that the Court supports the government in it's effort to pursue one-sided prosecutions in Uganda. So there is no guarantee that the furthering of domestic prosecutions really brings the ICC closer to the people on the ground.